I think one answer is that most of the higher quality carbon fibre tripods are using twist lock so you see more of them when you are hanging around with serious photographers.

But that is not a real answer - which came first.

Here is what I think the answer is: Compensating for a loosening mechanism is built in. What I mean is if you flip lever gets loose you have to get a tool to tighten it before you can use it. If your twist lock looses some of its grip you just tighten it more.

Having said that I had a Manfroto 190 for a long time too and never had a problem with the lock leavers getting loose. So it could be a solution to a problem that is rare.

As for faster: I don't think any penalty, if there is one at all, is big enough for it to matter. I can take a leg of my Induro twist lock tripod and loosen all three locks with one hand and then let the leg extend and reach down to tighten each backup. It is pretty fast. I never felt like it was slower.

Regarding frozen mechanism: if a lock sever is going to be unhappy frozen then a twist lever is too. I suppose they are less pron to collecting ice or mud that would block the leaver from closing.

One down side: whatever you do don't unscrew it too far. Nothing sucks more than having a twist lock come totally apart in crappy weather. Locking leavers are either open or closed you cannot open them too far.