lots of people only use premium bonds if they are a higher rate taxpayer or have lots of savings and have already maxed out an ISA
e.g. if you are an additional rate taxpayer you don't get a personal allowance so if you left your money in a savings account as you've recommended, have to pay 45% tax on any savings interest
so if you put £50k into your average easy access savings account with, say 4% interest, you'd earn £2k interest but would have to pay £900 in tax so would only actually get £1100.
MSE has a premium bonds calculator which says with average luck you would expect to win roughly £1,750* if you invested your £50k in premium bonds instead - i.e. £650 more every year*. Yes there's the potential you won't win that much - but there's also the potential you could earn significantly more, up to £1million.
Even as a basic rate payer, you'd have to pay £200 tax on your savings interest= overall interest of £1800. For the sake of £50 some people might prefer to risk the premium bonds.
Yes you could potentially earn more by investing in s&s but a) that runs the risk of losing capital, whereas there is no risk at all in premium bonds, and b) to get any real gains from investment you have to be prepared to invest for several years at a minimum. Often you can't withdraw instantly. Therefore people often use premium bonds if they want to have immediate access to their money rather than locking it away.
It's not so much you being negative that's the issue but being arrogant enough to assume that most people investing in premium bonds don't understand that they could earn more elsewhere.
Some people might very well just like the thrill of a potential win (fair enough) but many have made a reasoned (and financially viable) decision that is safer and will actually make them more money.