I think part of the answer to this question is in implicit/implied topics and the difference between the topic marker particle (
は) and the subject/object marker particle (
Though it can sound clunky and unnatural in English, the
Xは… can frequently be translated as "as for X, ...", "concerning X, ...", "on the topic of X, ..." etc.
Normally, who is being talked about is figured out by context, and so it can be omitted/elided:
(As for me, I) like taking baths.
(As for me), concerning taking baths, (I) like them.
(As for you), do (you) like taking baths?
(As for you), on the topic of taking baths, do (you) like them?
But (especially in places where it can't be figured out by context), you can explicitly mention who, e.g.:
As for Tanaka-san, he/she likes taking baths.
As for Tanaka-san, does he/she like taking baths?
風呂が好きです are possible, but in the case of
風呂は好きです I think I'd often expect to hear a
が after it like
風呂は好きですが,… "As for taking baths, I like them, but..." or something, and I think it's more common to use
風呂が好きです if you want to say "I like taking baths".
～は好きです can sound more general and
～が好きです more specific, which might be why you'd generally say
あなたのことが好き instead of
あなたのことは好き as I think the latter can be used in contexts like "I like you (but not specifically you)" or "I like you (but there may be reservations/conditions etc)".