Are you not missing some of the Morrissey singles?
Yes, but none of the ones I'm missing contain tracks that can't be found elsewhere. Any rare b-sides are found on the Singles boxsets, apart from "You Must Please Remember" - which is found on the "Dagenham Dave" single (which I own). I'm more concerned about having a collection that contains every NECESSARY release, in order to have every officially-released a-side and b-side. I'm not concerned about live songs or edits.
The only reason I have all the Smiths "best ofs" is because there are only a couple, and given that the entire Smiths discography is fairly scarce, I bought them all.