It's not the tech per se, it's that you have to open the app or at least unlock the phone (whichever it is), and people are more cautious with their phones compared to a card. They also tend to watch the screen instead of where they're going.
I can slap down my card with my arm outstretched, without breaking my stride, and before I hit the barrier it opens.
Observe a phone user in a London rush hour and it causes a noticeable backlog at gates