whats the benefit of a service returning an observable when performing a get or a post request towards mysql via php?

  angular, async-await, mysql, observable, php

this is a best practise and design question:
since the result of a php rest api is a single event (and a single value, when caught by an observable) does it really make sense to use observables in that case?
or, at least, is there a way to call a php rest api to get each single value, as an observed value? that would make possible the use of mergemap(), for instance..

just wondering because reading around seems that promises aren’t cool anymore..
but observables returning one event don’t seem to be useful, unless I’m missing something

looking for an explanation

Maybe the question seems stupid. Sorry for people who downvoted it: I’ve been trying to figure out the answer for months..
By the way, Is there any smarter/faster/conceptually simpler way to perform a (simple) select, returning just one value (an array actually), calling a "static old style php service" that stops sending data after performing the select, rather than using an observable?
Or, again, is there a way to take advantage of all the observable’s features even if the back end isn’t so modernly-conceived?

Source: Ask PHP