Paint bonds to a surface in 3 ways,by absorption, chemically bonding, and mechanically bonding. The surface in question and the type of paint/coating used will determine how well each type of bond will work, along with how well that surface is prepared. Any painter worth his salt will sand a wall or trim board before painting it, but many individuals and companies skimp when it comes to priming. This only serves to lessen the paint's ability to protect your home against the elements. Any paint will fade with age, however, failing to prime will increase that aging process exponentially. The primer job is to form a strong bond with the surfaces being painted,and in turn allows the paint to gain maximum adhesion to what ever it is applied to. Failing to prime is asking for early paint failure.
Primer is also extremely important when it comes to changing colors when painting. Primer blocks in the pigment of rooms that have been painted bright, dark, or vibrant colors. If you were attempting to cover a red wall with white paint and no primer, you could easily apply 5 coats of paint and still be able to see red. However. add a single coat of primer, and that will allow two coats of paint to cover beautifully. The primer can even be tinted in many cases in order to minimize the amount of finish paint needed even further. Beyond that, primer is essential when you want to seal in and block out the smell of smoke, pets, or other strong odors that have absorbed into a wall. Primer is your friend.
In closing,I'd like to suggest that you ponder a thought. Is it better to save 20-30% on the current cost of painting your home and have to repaint in 1-3 years? Or would you be wiser to spend the extra 20-30% in order to secure a coating that will last for 5-15? Your opinion matters. I welcome you to share it in the comments. Aside from that, thank you for reading. Be sure to call Clinton Painting Services the next time you need a painting related home improvement. Have a wonderful day.