Without precise time alignment, trying to provide bass from multiple sources could lead to interference patterns which would cause the low end sound to be way too loud in some parts of the room and almost nonexistent in others. Even if that weren't a problem, high passing the signal before sending it to the mains means that the mains have more power bandwidth available for the mids and highs.
You can always try it both ways and see if you have a preference in your particular environment. Personally I would high pass it and not even try it the other way.
As you move forward in the future with PA upgrades, you might consider a speaker management system that would include a crossover and delay for time alignment. Then you would actively cross over the FOH sends in the speaker manager and have separate connections to the tops and subs and then the high pass option on the subs will be obselete. I wouldn't go this route unless or until you have a snake with enough returns to handle it. Without the snake, it's very convenient to just run one cable to each side's sub and then run each high passed cable from the sub to the top.