Does not make sense or does it?

It resist electric and does high damage.

Grass has a single resistance to electric and Solar Beam deals massive neutral damage. Not as good as ground with double resistance and super effective damage, but still okay.

Ground types (like Rhydon) have relatively terrible moves and only decent attack at best. As such, you'll see high-dps neutral counters, such as Mewtwo/Dragonite/Machamp/Exeggcutor, in the rankings. Resisting Electric attacks is a plus.