While I understand your frustrations at not getting any drops and getting revs/spectral tasks. There are a fair amount of counters to your reasons.
Slayer drops are worth something because of their relatively low drop rate, increasing it by 1% would make it so that every 100 kills there's another drop, this may sound like something small but it's quite big. Tasks are often 30-70 kills, meaning every 2 task, there's an extra rare drop.
Revs and spectrals can be cancelled by getting an easy slayer task, it's bit of a pain to kill 50 ghosts, but it's certainly better than risking your items in wilderness.