YES, there are many reasons.

First and foremost - excess phosphorus and potassium in an otherwise well balanced soil - will make it WORSE.... It is likely just responding to a good dose of food...nitrogen and late spring flush/growth. Many yards ONLY need added nitrogen to do very very well (due to soil conditions)

Second (and maybe more important) - is that excess phosphorus is a pollutant - it is outlawed in many cities and states on established lawns (without a soil test).

However it could be that you are very short in phosphorus/potassium (P and K)... (like my soil).... however maybe just Potassium....? Or maybe just Phosphorus?

That is where a soil test comes in! :-) Then you can get a perfect fertilizer plan together and also check for some of the smaller nutrients like iron, boron, zinc, etc... its rewarding to know that you are doing the best thing for the lawn, not wasting money on starter fert, and also doing the right thing for the water systems/nature.

Good read from the Univ of Minnesota on fertilizers and effects/uses:
http://www.extension.umn.edu/garden/turfgrass/fertilizers/fertilizing-lawns/

Exactly! Phosphorus and potassium have very wide bands of acceptable ranges, but there's no reason to overdo it (doing so can cause problems). A $25 Logan Labs soil test will nail down everything about your soil and tell you exactly what you need to add.

Yeah, the problem is with using specialty products routinely and without good reason. Just because it worked once, does not mean the conditions are the same now. You need a soil test before you change the chemistry.