Sounds like your Dad might be the dim one...and possibley not as sucessful as he could have been... UK property has perfomed in line with equities if you look at the return over the last 20 years. And in reality many people's actual returns will have been far higher, as property is a often a leveraged investment. Put a £50k deposit on a £250k house that doubles in value in 10 years means that your £50k has turned into £300k. The rent pays the interest on the capital.
Try turning £50k into £300k on the stock market with a similar level of risk as equities. You can't. Unless you borrowed to invest in equities. In which case, find try and find a bank that will lend you £200k to dabble in the stock market ;)
And without landlords, where would people who need to to rent a property live...? There'd be no temporary homes.