> they can definitely rent a two-room flat alone and afford normal food just like everyone else.
Maybe where you are, but not where I am. Many people I know in full time employment cannot afford to rent a 2 bed flat. And that's regardless of where they're from.
Most of the tradesmen I work with these days are EU migrants come to London. Some of them are quite successful and have good lives, but many others really work hard to get by and do not have what I'd consider to be a life worth living. But they acknowledge that they're just doing it for half a decade or so and then plan to move home. Plans range from outright retirement, to starting a family and a business with the seed money from here.