Yes, I've yet to see anyone set out a logical rationale for why it's not a desirable outcome given the unpalatable reality of what formerly obese bodies tend to do.
Firstly, let me be clear, I have no objection to anyone on this thread or elsewhere being on WLI, for however long. I have no dog in this race. It's a discussion forum. This is a chat thread. I am neither fat or jealous. I can discuss Artemis 2 without being an astronaut.
In real life, I only know one person who is on them, though I could hazard a guess about a few others. It's none of my business. Though my one friend on them is looking alarming, has lost 7/8ths of her hair, and should never have got her hands on them as she has a 30 year history of severe eating disorder.
That aside, the issue with being on them longterm is, as I understand it, because of the potential over time for any of the serious adverse effects associated with them to occur. Also, because there are no longterm studies for the use of GLP-1s on weightloss specifically. There is realtime data for diabetics over say 20 years, but we won't know the cumulative effects of GLPs on other subgroups until we do. So many doctors with broader knowledge have urged some caution, but their voices tend to be swallowed in the swell of understandable enthusiasm.
Many drugs have unforseen longterm effects. So PPIs, necessary for millions, have been shown to have negative bone effects with longterm use, particularly with hip bones. Ditto, a surprise longterm effect of continuous use of SSRIs is bone loss, I've read.
Apart from financial reasons, I expect many people just don't want to feel nausea or adominal discomfort, if they have those side-effects and they have not really abated, over a long period.
A level of muscle mass loss, and bone loss that might lead to future osteoporosis, care of unsufficient nutrition intake on WLI has been put forward, as discussed earlier in the thread. Recently I read that some scientists have found there is an increased risk of some arthritic disorders with GLP1 drugs, which I found surprising. An old age full of sarcopenia, inability to get around, and with crumbling bones, would not be something to look forward to.
If, for example, some risks increase with longterm use of WLI, say muscle loss or pancreatitis or kidney problems, and the weightloss results of continued use start to plateau out after three or so years, as some studies have suggested, then the risk/benefit ration might change for an individual. I don't think anyone really knows the longterm safety or longterm benefits of these drugs used for weightloss. These things come out over time.
You could google these things, if you were interested. You could google the question, if you seriously wanted an answer. That's what I do.