During my first year of carp angling I caught nothing with pop-up and the thought they don't work was the obvious results.
What changes my mind was to fish with the right rig, from that moment I start to catch carp on pop-up boilies and the confidence rised up. I like to fish pop-up very low on the bottom, in this way it's not so different from a bottom bait.
What I found is that commercial baits are a bit hit and miss, they are water specific, in some work in other don't, and to discover which one is the right can cost you few tubs, instead when fishing with home made pop-up with the same ingredients as the free offering made a more consistent catch rates. I must add that my style of fishing is to build a confidence prebaiting regularly the water i fish, it could be the cause.