I do not carry a tube. I have ridden even 5 miles away! I do not know how to change my tire. And I probably need more grip strength to deal with my Pinhead locking skewer. I think there is a really easy way to deal with mechanical issues:
1. Have a plan
2. Carry your lock
If I were to have an issue, I have my phone. Know how to get home via transit from most locations in my 5 mile radius. I know where many bike shops are in the 3-4 mile radius. And I know where the secure bike lockers are. That is more than enough backup for me!