Because wages have stagnated and house prices have shot up
That's very true. And it doesn't just apply to the private sector, public sector wages were frozen for years and haven't caught up.
I work in the third sector, and all the projects staff work on are commissioned by local government or health. When I started (2005), the pay scale for the job I was doing then was 2.5 times minimum wage.
Once austerity hit, commissioners had to make cuts and as our services are non-statutory, they were among the first to be cut. Rather than make huge cuts in the service, the pay scales were reduced for new staff, and they have been unable to increase pay in line with inflation.
The rate of pay for that job is now 1.2 x min wage, so what was a relatively well paid job 15 years ago is now just a tad over min wage. In real terms, the pay has shrunk by almost 50%. As a consequence, we now give benefit advice to staff, as well as to clients.
There is a real irony that the staff are supporting families in poverty while they're precious little better off themselves.