How are they taking it away? There have always been people who rent and people who buy. Someone renting doesn't prevent you from buying.

How are the two related? It's not a zero sum game, there's new houses being built all the time.

If it's their only income source I assume they are retired. If they aren't, you are absolutely right.

They probably had a job for many decades, it's how they bought and paid the house.

If that's their whole retirement investment (as they said it's their only income, no idea about us retirement details) if they don't increase your rent, their net income will GO DOWN. Prices of everything also went up for them, if you think it's hard with constant income, imagine with declining income.

The value of their house going up is useless to pay for bread.

You should get a bigger paycheck, average wage growth is around 5% in the US, higher than inflation even.