Most medication is tested on men, as well, which is turning out more & more to be inappropriate, given that women can respond differently. OTOH pharma development & registration is SPECTACULARLY expensive for each drug approved, given how many fail ever to reach approval, so it's not massively surprising that in the past it's been a moderately generic test population. As I understand it, there's starting to be much more finessed R&D now in terms of personalised medication, but no idea when it'll become mainstream practice.
I believe that allergies generally are becoming more common, tho' I couldn't quote any peer-reviewed data on that. Anecdotes seem always to suggest that grubbier kids are less prone than the ones whose parents chase them around with cleaning products & anti-microbial gunk. There's always also the fact that these days medicine keeps alive some whom nature would previously have culled - harsh, but true - so maybe the allergies are higher in that sub-population? I can't imagine how expensive / complicated it would be to start testing everyone for antibiotic allergies prior to need, particularly given the excessive over-use of antibiotics & the corresponding increase in resistant microbes, which definitely don't need encouragement. Weirdly, my sister's mother-in-law was found to be allergic to an antibiotic last year which hasn't happened to her before - and she's well into her 80s. So maybe these things can also be late-onset? I've been to her house, though, and it definitely wasn't a result of excessive hygiene ...
I'm in the UK, so other than the embarrassment & associated downstream healthcare impacts of producing Andrew Wakefield, we're mostly pretty sensible about having vaccines done here. I know that MMR vaccine take-up fell off following that corrupt man's scaremongering, but I'm pretty sure it's coming back now to where it should be for herd immunity.
& you might rather like this quote:
Hee is a better physician that keepes diseases off us, than hee that cures them being on us;
preuention is so much better than healing because it saues the labor of being sicke.
(Thomas Adams, 17th C preacher)