It doesn't matter if he doesn't use Agility anymore, it doesn't mean he forgot it. Think logically, this is the anime we are talking about, not the games. When was the last time Team Rocket said their old motto, doesn't mean they forgot it or the last time Ash put his cap backwards before throwing his pokeball, etc, etc. I never really paid attention to how many moves were used during battles so I can't answer that.
Like I said, I didn't want to start any kind of argument, but can I just say that you came off a bit confrontational in both posts? I don't appreciate people confronting me with "logical" theories that they claim as fact and then telling me how wrong I am. Consider yourself warned for the following:
In fact, it
does matter to me that Pikachu doesn't use Agility anymore, because you can't cite any single instance in the anime that supports the claim that Pikachu can physically perform the attack anymore. It was never said in dialogue, the move was never demonstrated even when it would have been beneficial. Ash chose to have the move replaced with a different move to better fit his strategy. (That's another thing about your confrontational post that I'll address below)
Imagine how you'd feel if I gave you the written equivalent of an eye-roll because you didn't understand the concept of "Schrodinger's Evolution" ("Well it's obvious that you'd expect Jesse's Wobbuffet to not evolve. Like I said before, Wobbuffet undergoes Schrodinger's Evolution. It can only evolve into Giraffarig in the wild when it is being unobserved. Captured Wobbuffet and Wobbuffet that are visible to the human eye in any way, including the use of cameras, will not evolve into Giraffarig...only wild, unobserved Wobbuffet do. Didn't you know that? Come on, think logically. This is the Anime we're talking about, not the Card Game.")
Just because Team Rocket chooses not to do the old motto doesn't mean they're in the same category as a pokemon who learned a new move and doesn't use one of its old moves anymore. I have my car parked in my driveway. It's not running, but that doesn't mean it's broken down. Likewise, I can't hop into a broken down rusted car on cinder blocks and drive away. Just because both are motionless doesn't mean that both can start driving whenever I want to use them. One can start whenever I choose to start it, while the other physically cannot.
And Ash does have ultimate control over which moves are used. He's the trainer. If Pikachu could decide what movepool it was going to use, it might as well just ignore Ash completely.
If you just have a problem with the lexicon, say so. Yes, it seems foolish to think that Pikachu would have no recollection of ever using Agility, but if it never uses the move, you can't logically come to the conclusion that at any given moment it can and will use it again. If you sat in my driveway for a couple days, you'd eventually see me drive away in my car. At some point you'd have to accept that the old rust bucket on bricks just isn't going to move anymore.
Pikachu has not used Agility in years because it physically cannot. If you don't like the term "forgot," fine, but don't get confrontational and patronizing when you don't have any evidence to support your own personal imaginary cannon.