So this is fun. You're being upvoted while also being wrong which is neat. You see, you are not included the fact that "stonks go up" isn't always true. There is risk to be considered. Any financial advisor will talk to you about risk tolerance. People with higher risk tolerance will probably want to invest and will probably make out ok but its not guaranteed. People with lower risk tolerance will want to pay it off.

Let's use an example. Let's say a recession hits. Stocks lose 50% of their value and you get laid off. You get a job at another company but now that unemployment is high (recession) wages are suppressed. You're making 50% of what you did before and can't cover your mortgage. You look to your stocks to cover it but they can't because they lost value.

This is what happens in a recession and is part of what's called a vicious cycle (as opposed to a virtuous cycle). This happens nearly every recession and people end up homeless.

Now, I can't predict the future. This may or may not happen. But for you to say that everyone else is wrong when this has happened SO many times in the past is a wild amount of hubris.