I've remember Ash's six officially owned Pokémon: Pidgeot, Charizard, Heracross, Beedrill (now Casey's), Sceptile and Glalie, the ones that had never actually Mega Evolved for the first time despite their capability of Mega Evolutions.
Ash had caught Pidgeotto in the Kanto region, much to Misty warning him in her anger that it would consume his Caterpie. However, once Ash's Caterpie had evolved into Metapod, this prevented his Pidgeotto from consuming it. Right after his loss to the quarterfinals to Ritchie at the Indigo Conference, Ash's Pidgeotto later had fully-evolved into Pidgeot that he had released back into the wild, so that it could protect a flock of Spearow from the danger of Fearow, the one that Ash encounter as originally Spearow during the start of his journey in the Kanto region, although Ash had never Mega Evolved it into Mega Pidgeot for the first time.
Ash also had caught Charmander in the Kanto region, the one that its former Pokémon Trainer Damien had abandoned. Ash's Charmander had middle-evolved into Charmeleon that had become disobedient, and it later fully-evolved into Charizard that had remained disobedient until Ash had convinced it to become obedient to which it agreed. Ash had left Charizard at the Charific Valley, until it later rejoined Ash's Unovan party, and Ash left it at Professor Oak's Laboratory, although he had never Mega Evolved it into Mega Charizard X or Y in the XY anime series.
Ash had caught Heracross in the Johto region, and Ash left it at Professor Oak's Laboratory, although he had never Mega Evolved it into Mega Heracross for the first time.
Ash also had caught Beedrill at the Bug-Catching Contest in the Johto region. He had given it away to its new Trainer Casey instead in order to keep it in the party with her, although Ash and Casey had never Mega Evolved it into Mega Beedrill for the first time.
Ash had caught Treecko in the Hoenn region. Ash's Treecko had later middle-evolved into Grovyle. Later in the Kanto region, Ash's Grovyle fully-evolved into Sceptile. Ash had left it at Professor Oak's Laboratory, although he had never Mega Evolved it into Mega Sceptile for the first time.
Ash also had caught Snorunt in the Hoenn region. Ash's Snorunt fully-evolved into Glalie. Ash had left Glalie at Professor Oak's Laboratory, although he had never Mega Evolved it into Mega Glalie for the first time.
So, unless they have later changed their mind, why do you think that the Pokémon main anime staff writers have decided to not let Ash Mega Evolve any of his Pokémon, whether Charizard, Heracross, Sceptile and/or Glalie, for the first time at all? Do you think that they'll bring any of them out from Professor Oak's Laboratory to Mega Evolve them in the Alola Conference or later in the Sword and Shield anime series, or never, since Brock and Misty are the only two former main character to Mega Evolve Steelix and Gyarados into Mega Steelix and Gyarados, respectively? Please let me know, thanks.
Ash had caught Pidgeotto in the Kanto region, much to Misty warning him in her anger that it would consume his Caterpie. However, once Ash's Caterpie had evolved into Metapod, this prevented his Pidgeotto from consuming it. Right after his loss to the quarterfinals to Ritchie at the Indigo Conference, Ash's Pidgeotto later had fully-evolved into Pidgeot that he had released back into the wild, so that it could protect a flock of Spearow from the danger of Fearow, the one that Ash encounter as originally Spearow during the start of his journey in the Kanto region, although Ash had never Mega Evolved it into Mega Pidgeot for the first time.
Ash also had caught Charmander in the Kanto region, the one that its former Pokémon Trainer Damien had abandoned. Ash's Charmander had middle-evolved into Charmeleon that had become disobedient, and it later fully-evolved into Charizard that had remained disobedient until Ash had convinced it to become obedient to which it agreed. Ash had left Charizard at the Charific Valley, until it later rejoined Ash's Unovan party, and Ash left it at Professor Oak's Laboratory, although he had never Mega Evolved it into Mega Charizard X or Y in the XY anime series.
Ash had caught Heracross in the Johto region, and Ash left it at Professor Oak's Laboratory, although he had never Mega Evolved it into Mega Heracross for the first time.
Ash also had caught Beedrill at the Bug-Catching Contest in the Johto region. He had given it away to its new Trainer Casey instead in order to keep it in the party with her, although Ash and Casey had never Mega Evolved it into Mega Beedrill for the first time.
Ash had caught Treecko in the Hoenn region. Ash's Treecko had later middle-evolved into Grovyle. Later in the Kanto region, Ash's Grovyle fully-evolved into Sceptile. Ash had left it at Professor Oak's Laboratory, although he had never Mega Evolved it into Mega Sceptile for the first time.
Ash also had caught Snorunt in the Hoenn region. Ash's Snorunt fully-evolved into Glalie. Ash had left Glalie at Professor Oak's Laboratory, although he had never Mega Evolved it into Mega Glalie for the first time.
So, unless they have later changed their mind, why do you think that the Pokémon main anime staff writers have decided to not let Ash Mega Evolve any of his Pokémon, whether Charizard, Heracross, Sceptile and/or Glalie, for the first time at all? Do you think that they'll bring any of them out from Professor Oak's Laboratory to Mega Evolve them in the Alola Conference or later in the Sword and Shield anime series, or never, since Brock and Misty are the only two former main character to Mega Evolve Steelix and Gyarados into Mega Steelix and Gyarados, respectively? Please let me know, thanks.