Well, my personal take, based on experience, is this:

You have to have enough range of motion for the lift you are doing, if you lift and don't stretch, muscle tends to shorten, and eventually you are not going to have enough range. This leads to two problems:

1) Potential over-stretch under load and injury, which will require time to heal.

2) Pain in joins, like knees or shoulders. Goes away once you start stretching.

If you do some other additional activity which gets you through full range of motion, like yoga or some active sport, then there is really no need to do extra stretching, otherwise, for me, stretching is required.

Lifting is basically weighted stretching. You can't train a movement and lose mobility for the range of motion you're training.

If your training has at its core multi-joint compound exercises, you shouldn't have to worry about your mobility.