It supports the entire network and makes using applications possible in the first place. Why would YOU want to run it? You would be the only person that can answer that question.

As for me ... I chose to run my own RPC node because there are very few of them and I am an active witness and STEEM based developer that is trying to get more known. I contribute a lot of time and effort, and provide my skills as a system administrator capable of running, updating, and scaling a server such as the ones required for this undertaking.

Having a server with 100+GB ram at the very minimum becomes quite costly when using cloud hosted providers. It is far more affordable with personally owned and managed equipment, but this comes at a cost of having fire monitoring systems, redundant internet connections, power failover, physical space, and network bandwidth in tip-top shape.

So what do you choose? How much do you have to spend? What is your technical background?

All of these are necessary questions one must ask themselves when hosting production level servers for thousands of users.