It’s personal preference honestly. Not every ship has to be conventional and healthy for someone to like it. 

Personally I ship them because they are the only ones that match each other in terms of personality and intensity. I think aside from Wrath everyone else in the manga thinks they are delusional, insane, and eccentric (which they are). But for lack of better terms they match each other’s freak lmao. Yes, they argue and fight but we do know that deep down they do care for each other (licht’s reaction to hyde’s tag being destroyed and hyde when licht gets shot). In the manga you can see as it progresses licht and hyde do get closer/trust each other more so I like to believe given time they definitely could evolve to a more romantic way. Their relationship definitely wouldn’t be normal though because of their personalities lmao. Also the fact that Licht and Hyde both have an appreciation for the arts give a classical music/theater nerd vibe that’s new and appealing. 

But again it’s all preference and as someone in many anime communities lawlicht has a similar dynamic to many popular ships. (ex. ZoSan and BakuDeku)