Loaning enough money to you to buy a house is far riskier than renting an apartment to you. If you don’t pay your rent, I just have to evict you. If you don’t pay your mortgage, I have to repossess your house, evict you, then sell it at a loss.
So the standards are different for agreeing to that deal. For a mortgage, they want to see that you can handle life’s unexpected bills, like $3000 for a new transmission.
h/t Fun_Balance_1809