Real ones, or BMW? The proper Mini's were great. The BMW ones, not so much.
Were they bought from new, or low mileage, kept for long, serviced professionally and frequently?
Strange if it's BMW Mini, as it's no secret the R51/53 were absolute junk, and had many failures, such as steering racks, power steering pumps, gearboxes, amongst others, 99% of which require lifting/supporting the engine and dropping the subframe, costing you hours in labour.
I've seen all of those issues happen, on the same cars, it's just a matter of when, along with seeing JCW engine spin a bearing at full chat and take out the crankshaft with it

and that engine was FSH at Mini and was around 80K miles
The later stuff loves to snap a timing chain, along with the tensioner failing.
TBF, it's hardly surprising really, as BMW loves to do this with it's 'modern' engines of those era's and before them. For example, the N20 used in BMW's even had a major class action lawsuit, due to the obviously poor design.
You can take the oil cap off a 320i F series and actually get your finger in there and feel the slack of the chain (if you're lucky to catch it before the inevitable) and then when you drop the sump, you're rewatched with a knackered crank and bearings.
If you've had good experiences with them, then fair enough, I've just seen many at work pretty much financially write off the value of the car to the customer, thus not economical to repair.
Anyone that I've known to own one, that maintains them themselves, has wasted serious money keeping them 'reliable', and regretted it. And anyone that's paid someone else to keep them on the road, felt the same.
But fair enough if you and your friends have been lucky, but the enthuasist community, would definitely disagree with you from a financial POV to keep them as a long term car.
I'm not at all discrediting anything that you've said though mate, they're just one of those cars that you 'know what you're getting yourself into' if you buy one.
It is heartbreaking how bad modern BMW's are compared to the old skool stuff

You used to buy a BMW
because it had a chain, not be put off because it
has one! Modern cars are just built to last a lease/warranty and be thrown in the bin I guess.