what would be  the MAIN reason real estate is not for everyone, to
expensive for the average person to get into, or, the return rarely
keeps up with inflation?

I'm not sure about a MAIN reason, but for most people it's probably a
matter of coming up with a down payment and/or qualifying for the
loan.  Part of the reason real estate is/has been so hot is because of
all the new (& cheap) loans out there.  A 20% down payment used to be
pretty standard, but today you can find 0-5% down all day long. Plus
interest are near historic lows, so payments are more affordable.

There are several other reasons it may not be for everyone:
fluctuating income, don't want to deal with maintenance, not sure
where they will be in a few years, etc. etc.  One other great reason
is that it may be cheaper (even after all the benefits) to rent.  I
have a rental that generates $1200 per month income, but would cost
the tenant about $1800 per month to purchase even at todays interest
rates.  Plus they would have to come up with a down payment.  Just my
2 cents...