Tantos--or rather, American tantos (which is probably 90% of them out there, as opposed to a traditional Japanese tanto--are intended mostly to be fighting knives.
That's a good thing, in my opinion, because they don't do much else well.
The tip is designed to puncture deeply, but this requires a thicker spine due to the unique tip shape. A thicker spine results in a more tapered blade. So this means that a tanto may be somewhat dull, or tricky to resharpen. Some inexpensive tantos use hollow grinds to produce a razor-sharp edge that changes the geometry of the blade. Other inexpensive ones will have a sharp edge that doesn't last.
The belly of the blade often has a pronounced curve that makes routine cutting difficult--and the tanto is useless for prying, precision slicing, and careful cutting... frankly, for me, that's about 99% of a knife's jobs.
Don't get me wrong--as a fighting knife, even a cheap tanto can be very effective. Great penetration, and the belly helps open up wounds very well. But as a utility knife, that tanto will likely disappoint.
All the above are my opinions, and I won't take offense to any or all contradiction.