It's like everything else, it depends

If I ask a quote, get it, and answer only 2w later, I will probably apologize. If someone sends me a quote unprovoked, they shouldn't have any expectations of getting an answer, and if I answer even late, I won't apologize.

If my boss or people working on my project send me an email to get a status on something and it takes me a week to answer, I'll apologize- even if that's because I was busy on something more important. If a random colleague asks me for something unrelated with my direct responsibilities, similarly I'll get to it if I get to it when I get to it, and I dont think they should have expectations of receiving an answer, so I won't apologize