I could maybe see it for a shifter (needs alertness, endurance and emphasizes forms over spells), but warshaper has no feat requirement, nature's warrior only needs track and even daggerspell shaper just takes weapon focus(dagger) and twf (1st and 3rd feats.. leaves 6th open).
Given that spells are such a huge part of the class, if you could spend just 1 feat to ensure that you could always cast them even while in a much tougher combat form.... well, thats not something many people pass up.
Feel free to take a poll of druid players.
I agree with your premise that a druid without natural spell wouldn't be much of a threat if he could wildshape into a rat swarm, however letting a mage have a solar as a familiar would similarly be fine as long as he didn't use it, so thats not really saying much...