I watched the Pokémon anime when I was a kid. That was around the time Red/Blue were a huge thing. Like, really, back in the days everyone played Pokémon. Everyone.
As for today, it’s been a long time ever since I watched the last episode, but I do play the new games when they arrive and read some discussions on the internet every now and then. One topic that stikes me again and again is Team Rocket with their crazy obsession to steal Pikachu.
I’ve read numerous times, that Team Rocket is stupid for going after such a common Pokémon. I agree they could’ve had some seriously rare Pokémon to deliver their boss from what I heared, but the thing is… Pikachu is not a common Pokémon. It’s not super-rare either, but it’s still relatively rare compared to others.
In Pokémon Red/Blue you can encounter it in Viridian Forest with an encounter rate of 5%. The only place where it actually is common, is the Power Plant with an encounter rate of 25%, but you need surf to get there and it’s is a completely optional place to go. Chances are, on your first unassisted play-through, you don’t even know it exists, let alone go there. Also, it makes sense that all the electric type Pokemon are common in this place, it even has Zapdos, it’s such an electric paradise.
Gold/Silver: route 2 during the day and in the morning 5%
Ruby/Sapphire: in 2 areas of the safari-zone, both times 5%
D/P: Trophy Garden 10%
Black/White: not in the game
X/Y: route 3 5%, Santalune Forest 6%
There certainly are much more rare Pokémon (Feebas Gen III & IV anyone?), but Pikachu is not that easy to get. The easiest are Gen I (when you know where the Power Plant is + surf) and Gen IV. So while Team Rocket could try and focus on more valuable Pokémon, Pikachu is not that much of a crazy idea as people often make it seem to be. Just because Ash is running around with one all the time and the TV-series throws us this particular Pikachu in our faces non-stop, doesn’t make it a common Pokémon.