I remember the lotto lout!
He gave some modest (but presumably quite generous) amounts to others too so perhaps not all is lost for him, if he bought his parents or grandparents some property then presumably that is perhaps going to be passed back to him at some point.
Some people simply aren't functional at a certain level, not that the lotto lout was a full-on smack head/rough sleeper type but he was into drugs and he'd have otherwise been the nightmare ASBO neighbour type on a council estate or low-income neighbourhood.
Even a step up from that most people aren't very numerate and so won't handle a win very well, a financial advisor to simply protect people from themselves is probably useful in most cases + there is the issue adidan has highlighted:
Yup, even 100million isn't as much as people might initially think... the yacht & private jet are probably a bit out of reach... 5 million per year in service costs implies a 25million yacht, Learjet can cost like 10 million and also has high running costs.
I think from 20 million+ to 100-ish million is more the kind of lifestyle most people would associate with being a "millionaire"; at that level you can legitimately buy a big mansion house in the countryside, urban penthouse and supercars + fancy holiday home and spend money day to day like a high earning salaryman/exec without needing to worry about future income + can buy small businesses/be an angle investor etc.
But it's not really enough for your own superyacht and new gulfstream so given that , I think the euromillions prize is fine, the higher 100million+ prizes are simply a function of rollovers but in a regular draw you really want to be winning an 8 figure amount not a 7 figure amount if you want to feel like a "millionaire".