Why do people like pokemon games so much?

I mean, if you just use your starter pokemon, he'll level up way past every other pokemon you ever have to face. Theres no real challenge in the game; mostly you just wander around, exp-share leveling your pokemon or looking for some rare pokemon. Why do people find this fun?Why do people like pokemon games so much?
first of all you cant just use your starter. even if its high leveled there is type ratio. if you chose a grass starter there are at least 4 types that are super effective against it. and people find it fun just because they like pokemon