If I remember correctly the military / aerospace shy away from this spec because the connector with the pins is on the backplane, with the sockets on the cards.

So if you incorrectly insert a card and bend a pin you're in trouble.

VPX has the sockets on the backplane so avoids this issue, if you bend pins you just grab another card from spares.

This may have changed since I last looked at it.

Telecoms industry definitely seem to favour TCA though.

I don't know, I work in particle physics and here µTCA is all the rage nowadays.