This is like bitching that a cooking class shouldn't teach people how to make meat because it's not useful for vegetarians. Being more inclusive would be a fine thing to do, but I'm not going to wring my hands if something's only suitable for 97% of the population.
(
Also, yes, 2-3% is consistent with best current estimates. There are ~1.5-3% that are gay and a few more that are bi. Obviously straight dating advice is useful for bi people, so there's no reason to count them separately here. Likewise, trans people generally want to act like their identified gender, so straight dating advice is generally fine for them as well.)