If I’m not seeking an answer to the problem, the people I choose to interact with are typically good at reading that fact. I don’t generally get a lot of unsolicited advice except, say, from my parents who just kind of seem to come with the instinct to offer advice everywhere. In other cases “why don’t you just” is a valid response to me and sometimes does address an obvious solution I didn’t know about or had completely missed. So in my case? I dunno. 50-50. Though I don’t usually hear that phrasing. It’s more like “Well, have you tried …” or “What if you …” Overall, though, personally I don’t have a problem with the phrasing “Why don’t you just” as it generally leads to trying to brainstorm the problem, in my experience with the people in my life.