Why did old TV shows used the same actors over & over ?

I’d think the actors had a contract with the studios and this was the a way for the studios to fulfill this contract and give them them airtime the were due or get the most out of them (probably more likely).
I’ve seen on old episodes of Culumbo, for example, George hamilton !V played at least 2 different episodes, as did a few other actors. Maybe in those days their appeal was strong enough to get away with re-casting them?
It’s a good question.

Scotsbloke gives some good reasons. Another is simply that certain actors were available and affordable.

That might because they can’t afford to pay another actors,or it could be the policy of the show toward the actor(that won’t allow him to appear in another show except in his particular show). Another reason is that some people just love to see certain actor in their favorite show so this could cause TV show production to keep the same actor from time to time.

The production company may have had an executive who had or the show’s star may have had a relationship with that actor that caused them to use him or her multiple times.

Good answers above, but this still happens, it’s just a bit less noticeable. I have friends who have played numerous roles on Law and Order and its spin offs. I wonder if perhaps the field is more open now, with the studio contract system gone and a strong Screen Actor’s Guild. It seems like there are an awful lot of decent actors out there getting at least a little T.V. work.

How about popularity of the actor/actress. people, even today, have their favorite actor, just like their favorite recording artists.. it may have been about their contracts with the studios, but it was also about using peoples favorite actors in order to bring in revenue. could it have been all about the money?