I think a lot of the more modest winners (say, >%5million) also fall into a mindset where they thing they are rich (and they are). But they equate rich with "can afford anything". But they only walk away with $2m (taxes and lump sum). If they drop $750k on a house and even "just" $150,000 on a couple cars, it's nearly half gone before they've even lived.
When you look at it at that, it is easy to see how it can all be gone so quickly. All the see is that they are rich and they assume that means they'd don't have to pay attention, so they don't notice the balance dwindling.
Really, $2m isn't that much. I mean, of course it is, but at 4% it's $80k/year. If you start with very few assets (so still paying rent or a mortgage, need a buy a car, etc.), that's only a solidly middle or upper middle class life. Which is of course sufficient, but not for someone who feels they are now rich and wants to live accordingly.
If I won $2m (walk away with $) tomorrow, my life would change very little precisely because long term, it's $80k/yr, in my mind. Husband would still plan to retire from them military at the same time (in a few years). Any thoughts of a short second career would likely be out, but that and maybe being able to afford to live in our dream area (but probably still not) would be the only huge changes. Likely nicer presents for everyone at Christmas.
Because while it would be incredible, it isn't enough money to bump us up into a new lifestyle, really.