im not retired however i entertained the idea a couple years ago of moving to downtown in my city and realized how just that move from a house to an apartment was going to impact my lifestyle.. sure there are close-by walk / bike paths, restaraunts, shopping, coffee, museums, and other activities.. however my love of building things would not be able to take palce without a garage / shop.. things simple as my over-the-top christmas displays would cease, no more futzing and playing with my home automation, nor hosting big dance parties in summer and Christmas parties (apartment life requires reserving the single party room in the complex and hope you win it the day you want it).. while yard work isnt my favorite thing it does take up time in the summer. and is a good source of sunlight and exercise.. i wouldnt have that anymore..
if your idea of retirement isnt home-centric.. ie you make and sell trinkets at festivals, you bike, hike, musem-hunt, explore cities, towns, and the outdoors, maybe are foodies and want to travel around trying out restaraunts on your bucket list, etc then I can see bus life as being excellent for the first few years of retirement. but then eventually setting down a homestead someplace.. or perhaps buying land where you can live for months at a time before embarking on another journey.. god forbid someone has a medical emergency or needs a surgery , etc having some sort of base where you can have "down-time" is a huge plus..
I don't see it working for those who like to build things, collect anything, or even entertain (again unless you have land to entertain on)...