Reason #2: There may be legal problems with the title to the property. Most people now hire home inspectors to check out their dream residence for fatal building flaws. Your lawyer is there to help minimize nasty surprises over fatal legal flaws. Like that there's a registered right of way for an oil pipeline through your backyard. Or that half the garage that comes with the property is actually located over the neighbour's lot line. Or that two liens for non-payment of large debts are registered against the property.
Reason #3: You need to borrow money to buy the property. Very few of us are able to pay cash for real estate, unless we're buying bare land or a really run down house in a very cheap location. But anyone lending you a large sum of money to buy a property is going to want to register a mortgage against the property to secure the debt. And placing a mortgage on a property requires a lawyer, in part to make sure there aren't other priority claims already registered against the property in which case your lender might not be willing to lend, or might only lend at a much higher rate of interest if it doesn't get first priority against the property.