Depends on if your soil needs P and K. It is possible to have plenty of one or both.
N does need to be added for ideal growth.

 

In addition to the possibility of not needing P or K depending on your soil levels, in each 50 lb bag you are generally buying 23.75lbs of limestone chips as filler and 4lbs of chloride in the MOP plus the cost to ship those items. A 19-19-19 would be more cost effective if you needed N, P, as well as K. Limestone is often the hardest raw material of which to control the moisture level, which may contribute to spreadability issues in some cases.

 

There main reason to not use 10-10-10 NPK as your regular lawn fertilizer is because your lawn does not consume those nutrients in a 1 : 1 : 1 ratio. The ideal ratio of N-P-K for lawn fertilizers are much closer to 3 : 1 : 2 or 4 : 1 : 2. (I tend to lean toward the latter because I push growth during spring and fall)

If you put down 10-10-10 only once a year, you would probably be fine, so long as you make the rest of your applications high in N, zero P with some K.

If you only put 10-10-10 down and only did it once, you lawn will be starved for N the rest of the year.
You really want to tailor your application of fertilizer to match the growing needs and what is best for your lawn at that time.

Here is what the interwebs say about excessive phosphorus...
The buildup of phosphorus in lawns, gardens, pastures and croplands can cause plants to grow poorly and even die. Excessive soil phosphorus reduces the plant's ability to take up required micronutrients, particularly iron and zinc, even when soil tests show there are adequate amounts of those nutrients in the soil.

And here it what it says about excessive potassium...
Potassium does not deplete the water of available oxygen as do some of the other elements contained in fertilizers. Excess potassium is relatively harmless to the lawn and the environment, but too much potassium likely also means an excess of nitrogen and/or phosphorus, both of which can be harmful.