> It's curious to me that so much of the focus on COVID vaccines focuses on the antibodies produced immediately after infection and vaccination and so little on the longer-lasting immune responses (memory T and B cells).

Lol it really isn't curious. The vaccines do really well at the first metric, and it can be measured in very short trials (which means smaller trials due to less attrition, and means more trials, etc.) The second metric, they don't do so well at and it's more difficult to measure. It'd be curious if things were any other way.