The "should" here is a red flag for me. By what criteria should we? It's clearly pleasant, but toward what other goal is it useful?

Hm, I tried to explain why in the next sentence:

The magnaminity, compassion, competence, acceptance, and feeling of awesomeness created by the jhanas should be cultivated and drawn upon whenever possible.

I just sort of assumed people would think of those as useful traits to have if possible. The Buddha was hella competent.