Personally, I tend not to like these sorts of questions at least for most non-sales positions. They show up rather often as suggested questions for people that are interviewing for roles in sales so, as with most anything that involves interpersonal interactions, it will depend on the individual. Based on your profile, you appear to be looking for IT positions-- I would tend not to ask that sort of question for that sort of position.
Most interviewers want at least a bit of time to organize their thoughts and get their notes together after an interview before passing judgement. Particularly if you met with multiple people (either serially or in parallel), those interviewers are going to want to get their thoughts together, compare notes, and come to a conclusion. Giving an off-the-cuff answer can be a bit off-putting.
When I'm involved in the interview process, I'm generally doing the technical round of interviews. My goal is to get an idea of where a candidate is strong and where the candidate is weak but it's generally someone else's job to figure out how to prioritize those things. I don't necessarily know which strengths the hiring manager is ultimately going to prefer and which weaknesses are going to create the biggest obstacles. I can certainly guess (particularly if the interview went badly and the candidate is weak across the board). But those guesses might be wrong.
An interviewers biggest concerns might also feel rather unfair to the candidate. The "ideal" candidate for most IT jobs doesn't exist-- they're an expert in the precise half dozen or so major technologies that the company happens to use who also has a deep understanding of the company's business area and possesses exceptional interpersonal skills. And this mythical ideal candidate is willing to take the job for the salary that you have budgeted. Everyone knows going in that this person doesn't exist so comparisons to the ideal candidate don't do much good. They also tend to be very unfair in a lot of ways-- an interviewer often knows from the candidate's resume that the candidate doesn't have certain types of experience. They may interview them anyway because what they do have may make up for it but the biggest concern could well be something that was obvious from your resume. Telling someone that doesn't list technology X on their resume that our biggest concern after an interview is their lack of X might be truthful but it's not going to make anyone feel good.
For companies that have multiple open positions, there are also situations where people are trying to "mix and match" skills across candidates which makes feedback even harder. Imagine I'm a hiring manager who has two open theoretically identical positions both looking for skills X, Y, and Z. If you apply and have great X & Y skills but no exposure to Z, that may be fine if I can hire someone else with a lot of Z. On the other hand, if none of the good candidates have a lot of Z, I may prefer to take a couple of people that have an intermediate understanding of X, Y, and Z hope that they can figure things out between them rather than having two experts dividing the tasks. The issues with your candidacy may well change depending on the skillset of other applicants.
Finally, answering those questions truthfully is often rather uncomfortable. Telling someone that you don't think they're anywhere close to the skill level that you need and that you're going to be strongly recommending against hiring them would be brutal. Telling something that you're on the fence about who you might want to extend an offer to depending on how other interviews go that you really wish they had a bit more experience with some technology or that you were hoping from their resume that they had more business knowledge doesn't get the new relationship off on a good foot. It's hard for the candidates not to take that as an attack and defend themselves (which rarely produces good results). And it may lead the candidate to have a bad taste in their mouth if the company does extend an offer. If you do ask these sorts of questions, most people are going to reply with vague platitudes that communicate as little as possible in order not to offend anyone and to avoid making any rush judgements.
Ideally, of course, the hiring manager would reply with a concern that you can quickly address. But that assumes that the hiring manager is so poor at their job that they have a major concern that they can articulate for which they don't ask enough questions to give the candidate a fair chance to address. If a hiring manager knows that X is an impediment to moving forward, they had darn well better ask questions about X that are designed to let the candidate either address or confirm the concern. Perhaps there are occasionally situations where the hiring manager misunderstands something that the candidate said and that misunderstanding can be quickly rectified at the end of the interview. But that is exceedingly rare.