Even if you blow off your rocks, vacuum your sand bed and vacuum your sump every week, the material has been sitting there breaking down and adding additional nutrients to your system all week. With filter socks you can relatively quickly and easily swap it (them) out every couple of days and break the nitrogen cycle that would have taken place with all of the material that gets caught in the socks. Same concept as your protein skimmer, but instead of targeting DOCs, filter socks target solids, that for the most part your skimmer would never successfully process, and are likely to gunk up your skimmer pump.
Changing socks should not take more than a couple of minutes every couple of days. If that is too much time then I suspect that there are plenty of other things you are not doing for your tank.