I never seem to get around to it. I did use a liquid fertilizer on a small section of the garden this year and fully intended to do the rest, but there's never enough time to get everything done.
If I ever do get really efficient and start fertilizing on a strict schedule, I should be able to get along for years with just the stuff that's already on the garage shelves. I have no problem buying all types of fertilizer. Actually applying it is a different matter, however.
I've always suspected that it might need doing, so that's why I'm giving it a try. If I continue to see no difference, I'll happily give up.
Any discussion of chemical fertilizers always reminds me of the old story of the snake oil salesman who was selling people a super-duper fertilizer. It did have an almost immediate impact on the health and vigor of plants. The reason, however, was that the absolutely useless stuff he was selling had to be applied in conjunction with copious amounts of water, and the water was restoring the health and vigor of the plants.