Yeah each temple has its speciality.

Every family has a "kuladeivam" which is basically a temple for that (patrilineal) lineage. Every family has one. Every temple has few families.

Then it's special for people in the same town as the temple. Modern migration makes this a different set from the one above.

Then each temple has special events on specific days/week/month/year.

And then on top of that some few hundred temples are special in general and are crowded 365 days of the year with people from all over.

Adds up.

> Must worship take place in a temple?

Just my understanding. You can worship anywhere even in your head, but temples are one thing which improve "quality" of worship by a lot. The logic roughly goes - since most people aren't capable of high (enuf) quality worship in their head or at home, temples help them. More of a magnitude thing rather than a binary thing.