Learn Spanish (Spain): El sastre siempre pide las medidas. - The tailor always asks for the measurements.

English uses "ask" for two different things, but Spanish separates them. You use preguntar when asking a question to get information. You use pedir (conjugated here as pide) when requesting an object, a service, or a favor. Since the tailor is requesting the measurements so he can do his job, we use pedir.

Why is there no word for "for" after pide?

The verb pedir translates directly to "to ask for" or "to request." Because the concept of "for" is already built into the verb itself, adding a word like por or para after it would be incorrect.

This lesson is about polite requests with quisiera. Why isn't the imperfect subjunctive used in this sentence?

This sentence is stating a factual routine about what the tailor does in the third person, so it uses the standard present tense. The imperfect subjunctive is used when you are directly making a polite request. If the tailor were speaking to you right now to soften his demand, he would use the target grammar: Quisiera las medidas (I would like the measurements).

Does sastre change depending on if the tailor is a man or a woman?

El sastre refers to a male tailor. If you are talking about a female tailor, you would typically just change the article and say la sastre, or use the distinct word for a dressmaker, which is la modista.