I really hate this mindset. I rented for about a decade. Renting allowed me to bounce around from job to job in various cities and grow my career. Had I owned houses during that time I would have lost money due to the transaction cost overhead. I was also not responsible for any upkeep, which I'm not well suited for anyway. Oh and I absolutely did invest. My money was simply invested in the stock market which had a far higher rate of return than the housing market.
I own today, but I'm well ahead of most of my peers that bought houses right out of college.
Yes people who move often shouldn't buy. No disagreement there. But that's like saying that you shouldn't invest in stocks because if you sell in a year then it's probably at a loss. Investments are to be held for a long period.
As for investing: you invested what you had left after rent, but you didn't invest what you paid in rent. With a mortgage, you are investing the mortage payment minus interest, and you can still invest what you have left.
I own today, but I'm well ahead of most of my peers that bought houses right out of college.