It depends on the situation.
If you get some kind of sucker fish to keep your rocks and glass clean it will eventually run out of the miniscule amounts of algae it's been recruited to clean up and will need plenty of it's own food and make plenty of it's own poop to sit on the substrate and for
you to clean up. The same time you're spending sucking out the extra amounts of waste the little "cleaner" puts out could be spent equally and as easily with just a couple scrubs here and there with a toothbrush and fine-edged card or razor blade.
If I'm having gnarly algae issues and need a real good algae eater I'll go for a bushynose, some otos, siamese algae eater, florida flag fish, mollies or whatever the compatibility issues call for. But I have to make sure I can dedicate that fish a permanent home and make sure I'm aware of the fish's permanent needs and can supply them.
I don't overfeed so I have no use for keeping a fish that will "take care of leftovers".
I clean the substrate regularly so there's no need to have something shuffling around down there.
If I want something for aesthetic reasons I'll get them. I have cories, loaches and plecs. They're not "cleaner fish". They require their own diets and add to the bioload accordingly. They make more of a mess than they'll ever help clean up.
And while I don't agree with the logic of "cleaner fish" I can very much agree that it's hard to have a tank without a bunch of cories, loaches or plecs to make it feel complete.
