The quickest answer is: Luckily, you don't have to trust us!
These both ensure that your keys never touch an internet-connected device, which means we couldn't steal them even if we wanted to or if our site itself was compromised in some way.
That said... our team has been in this space since 2015. We don't do this for the money and we certainly aren't going to risk our reputations, hard work, and lives for money.
ETH is going to the moon as it is... we just have to keep building for the future and we can have it all. :)