Pichu is a very weak and obsolete Pokémon among trainers, so if a trainer owns a Pichu, it's because it's trying to learn Volt Tackle, and it was born in captivity.
Pichu, though weak, is very good at hiding from prey and doesn't need camoflauge or the like due to its size. Alot of trainers who don't catch Pichu still think it's very cute.
Pichu is a very
overrated popular Pokémon among the anime community, the Pokémon fanbase being part of said community. With that being said, don't expect to see a chat that doesn't have a person with a Pichu icon.
There is also an elusive Chatango account based on Pichu. Even though the account is never used, the owner of the account doesn't want to sell it. He's making a mistake, because some Chatango users want to hack the account to use it themselves.