The difference is Travolta and others are earning 10’s of millions per year from passive income (royalties in their cases) on top of their existing massive pile of money which is also generating investment income. They are also generating other income from new firms and songs/tours every now and then too. In other words, they are considerably richer than a lottery winter with £180m.
With a lottery winner it’s basically once and done, you’ve got what you’ve got and you aren’t getting any more. A huge number of lottery winners blow their entire winnings far faster than they ever imagined because they think they have enough to live a Taylor Swift lifestyle while not realising those celebrities are much more wealthy than them due to their active and passive incomes.
£1m isn’t much backup money either but I guess it depends how old you are. Once you get used to the jet set lifestyle, reigning it back in is difficult. Just look at how many sports starts are going bankrupt in retirement.
Inflation is also the enemy and most the interest you get off your back up money will need to be reinvested just to maintain its value.
A middle earner winning £1m wouldn’t need to worry about money again but they couldn’t expect a material change to their lifestyle unless they were well into their 50’s let alone even think about retiring. At my age (30s), couple of middle earners would probably need at least £3m before they could even consider it.