itch.io

1-

This is called redundancy, normally the same provider can offer it to you, since they usually have several data centers around the world, but it is more expensive and it can always happen that something fails.

Having everything replicated in 2 companies is obviously twice as expensive.

Maybe for you, having and paying monthly for 2 ISPs is not significant, but deep down, you are burning money, because a single ISP usually works over 99% of the time, so only 1% costs you 50% of your internet account.

Paying an additional 50 dollars a month is not the same as practically doubling the costs of a company in an area ;)

2-The best thing is the experience, create your own data center and sell the service to Itch, if you can do it better and cheaper than what they currently have, we will all thank you.

3-

Maybe they pay for more redundancy or you haven't noticed their downfalls. I personally don't find Itch to have been down long enough to be annoying or worrying.