They don't recommend because they don't see clear evidence in outcomes. See my EMA link below. This doesn't make the recommendation any closer than recommending not to.
The booster is an approved and safe procedure, but it confers no benefit unless you have risk factors.
[1] https://www.ema.europa.eu/en/news/ecdc-ema-update-recommenda...
Just because a drug is approved doesn't mean you should take it indiscriminately. It is "safe" to drink NyQuil every night. Doesn't mean you should. If it confers no benefit to you in your unique circumstance, you shouldn't take it. Hence, the booster is not recommended for certain groups - because it is not needed and provides no benefit.
https://www.fda.gov/drugs/information-consumers-and-patients...
> If the Phase 2 trials indicate that the drug may be effective--and the risks are considered acceptable, given the observed efficacy and the severity of the disease--the drug moves to Phase 3.
This year it appears they've approved 30 and last year they approved 50. That's quite a few.
That is exactly the point that I made above.
And where does it so clearly state in the website that second part? And of course it's ok, but that doesn't make it a recommendation.