Running for state house in my area is about a 100k-300k proposition. On top of that, you need a team that can handle a campaign. You need a message that resonates. You need to spend every free second doorbelling, fund raising, or other election related stuff.
If you want to start lower, say city council, it'll cost a lot less, but take just about as much of your time. On top of whatever it is you do for a living. And as a city council member, you get precisely zero say in national level issues. You deal with parks spending, development, budget issues, etc. Which is great stuff, but not what is upsetting the general public right now.
A local mayor told me "just don't plan on seeing your family for six months"
If you want to run for any sort of office, you have to have a lot of money (or access to the kind of people who can give you money), the kind of job that doesn't demand a ton of you and is flexible in terms of scheduling, and the personal freedom to do nothing but work and run for office for a long time.
Those are some reasons.