Isn't GitHub Enterprise self hosted?

I'd imagine the main reason to go with GitLab is that it's free. GitHub Enterprise costs more than Stash (although it offers more).

I thought not, but maybe I'm mistaken?

I know that there is some payed service that isn't self hosted.

That's a silly reason, where do you think your emails, facebook, twitter feed is hosted? I trust US companies over any other.

Out emails are hosted on our company's server. Facebook and Twitter are publicity channels with public information only. And we don't even have that important corporate secrets.

You might trust US companies, but after Snowden many people don't trust the US anymore (industry espionage). And there is no reason if you aren't a one man shop to not host such things yourself.