Simple answer - because you cannot compromise the value of your home. A shoddy painting job can turn off even the most interested buyer and make your home's value plummet significantly. Yes, it is admirable to want to do the whole thing yourself and not have to pay professional painters to do something you've probably done before. But here is why hiring a contractor would inevitably be the better decision on your part get more info.
First of all, painters are specially trained individuals who have experience in a variety of different projects. The average homeowner probably has some basic house painting skills, but very few of them would measure up to somebody who actually paints for a living. And I'm sure you will agree with me that you, as a homeowner, have better things to do than spend the whole day painting your home, regardless of the reason. You'd rather have someone do it for you while you focus on other matters.
Secondly, painters will make sure that your home has the proper finish that would protect it from wear and tear. A sub-par painting job won't do much to defend your home against water damage, mold, rust and other external factors that could decrease its value. You would want your home to last as long as possible, and having the pros do the painting for you is one way to increase the chances of this happening.
The third and fourth primary reasons to hire professional painters would be convenience and safety. Going back to the point we made earlier, it can be tiring to do the painting yourself. And we haven't even mentioned the chances of getting your clothing permanently stained or the possible injuries that may occur should you be working with ladders and painting the second story of your home.