Even if you saved that 100-150 euro every month,
you'd not afford buying it after 30 years, assuming
it stayed at the same price-point.
The thing is that many people don't have an extra 150 euros per month (not to mention ~50k euros for the down payment) to save or invest in a mortgage, they spend everything they earn every month even when renting.
If you're in a position where you have extra money and you can choose whether to invest it in the stock-market, buy a nice car, or put a down-payment+mortgage on a place to live it's a different consideration.