Does anyone know why on TV show's credits a lot of times the actor's first name is lower case and their last name is done in all caps?
It's really just a design choice.
Part of the reason is that it makes the big blocks of text in the credits a bit easier to read and easier on the eye. Also, an actors surname can be considered the more important identifier than their first name. For example if I say Brando, Chaplin, Olivier, Nicholson, De Niro, Pacino, etc. etc. you know immediately who I am talking about.
Similarly, in many countries actors unions require professional actors to have a unique name to avoid any possible confusion as their name is a key part of their professional credibility. In many cases, they will stick with their given first name and pick a distinctive surname if their original name is already taken or they just want something which sounds better.
Equally, it is fairy common practice to refer to actors by their surname in reviews and other theatrical journalism.