Ash has been based in Kanto this whole time without seeing Misty and Brock and flew to Hoenn without seeing May.

[POKEMONMASTER260]

I know he saw Misty and Brock in the last series, but he's actually been in Kanto this whole time, (albeit flying to different regions a bunch of time,) and hasn't seen his best friends once. He didn't even bother seeing May when he went to Hoenn. It's just a symptom of the fact that the writers just want to reset everything every series and don't care about people actually getting invested in anything. But this is ridiculous.

 

[Lysander]

May is probably travelling through a different region right now.
I wouldn't be surprised if Misty and Brock made at least one appearance this season. They seem to be the only former companions the writers care about now considering none of Ash's XY companions came back in Sun and Moon and none of his Unova companions appeared in the XY series.

 

[QuietDragon]

May went to Johto back in the end of AG and briefly went to Sinnoh in DP! Keep in mind that Ash's friends are not static, they are living their own lives, going on their own journeys off-screen. ^^

I am sad they didn't meet when he went to their regions, but there absolutely must be chances for that in the future!! Others have mentioned that in previous series, it usually took about around 40 episodes before old characters reappear.

Misty and Brock recently did appear in silhouette form!

The writers and animators, from what we see, do love the old charactera (Iwane Masaaki-san and Shinohara Takashi-san are always drawing older characters on their respective twitter, expressing their wishes to see them again, Iwane-san drew and coloured and animated Shinji/Paul in SuMo style and drew a beautiful Iris in her Champion dress wishing to see her return in it in the anime...), but the executives only care about promoting new games, typically...

There recently was Lt. Surge telling everyone about Ash, so there is continuity yet! I really do hope that with this series taking such a different approach from past ones, there'll be more scenes with older characters. We didn't get that in the second anniversary movie, despite the director considering it, so this series would be best to showcase old friends and rivals.

 

[Palamon]

Something I do know about May is that her Japanese voice actress doesn't voice act anymore. I feel like this contributes a lot to her never returning, besides the "reset button" thing, or whatever. It's also true that May could still also be travelling in other regions. I guess the same could be said about the rest of Ash's old companions.

 

[QuietDragon]

Something I do know about May is that her Japanese voice actress doesn't voice act anymore. I feel like this contributes a lot to her never returning, besides the "reset button" thing, or whatever. It's also true that May could still also be travelling in other regions. I guess the same could be said about the rest of Ash's old companions.

KAORI (her Japanese voice actress) was sick and it changed her voice, so she no longer sings. I think she briefly returned to acting, but nothing long term...

Yes, in 2014, she narrated for a youtube channel!

Some other actors retired, I think Shigeru/Gary's is one...

 

[Kuzehiko]

Them all have different goals so it's obvious they're busy and can't see each other whenever they want. That should be the reason but I hope May comes back for future episodes. She hasn't appeared in the show for 13 years up till now. I don't care about Brock or Misty.