Divine Smite doesn't need help, but how often do paladins use these smite spells instead of just Divine Smiting?
My paladin has used Wrathful Smite with some success a few times, but it's pretty situational and it's rarely the best option. If you have preparation time, then Bless, Protection from Evil, or Shield of Faith are much better uses of your Concentration slot. If you don't, then it has its uses in debuffing enemies (like giants) too powerful in melee to go toe-to-toe with, and who have enough hit points that the difference between 1d6 (Wrathful Smite) and 2d8 (Divine Smite) isn't going to make a major immediate difference. Even so, Command ('flee' or 'hold') is usually a better option because you can use it at range, it doesn't eat your Concentration, and if it works, then it may provoke an attack of opportunity as your target flees, as well as actually stopping your target attacking rather than just giving them disadvantage when they attack you (the 'can't move closer to the source of fear' element of the frightened condition isn't much help when you have to be in melee to use Wrathful Smite in the first place!) Wrathful Smite's longer duration is a plus, but again, that's concentration-dependent, so it's not something you can rely on and it comes at a not-insignificant opportunity cost. If you're alone or have limited allies in support, however, Wrathful Smite can be great because unlike Command, you can actually attack as normal while it's active.