What, you don't know what additional danger and problems do higher voltages pose? Do you see those giant insulators on the powerlines above? You know what insulators do, right? Effectively, they help create a safe zone around a wire, where there should be no grounded objects, and for 25 kV this zone is significant. Even cost and bulkiness of the insulators aside, there might be not enough space in the city with other infrastructure incredible tightly packed to fit this safe zone in.
And what about EM induction? 25 kV creates considerable currents on any metal surfaces within a few meters. I even experienced it myself, touching a handrail (which should've been even grounded BTW) within, like, three meters from the 25 kV AC contact wire. It hurts! So yeah, the pedestrians would be thrilled to walk on an old low bridge with 25 kv AC wires directly under it biting them with the induction. And all the sensitive equipment? Road radars/cameras, traffic lights, they all should have been well shielded. That's an urban planning havoc to think about it all even if everything goes right.
And if it does go wrong, say, a ripped wire (happens all the time on trams!) or a short circuit in a crowded space? Have you ever heard [s]of the tragedy of Darth Plagueis the Wise[/s] about the stray voltage?..
The railways always have (or at least should have) an exclusion zone around them, even in the city. What exclusion zone are we talking about when speaking about the tram, especially not the fully isolated LRT type?..
And then again, all this mess for the benefit of having less power substations in the urban area where you have power literally everywhere.
Sorry if that sounded a bit snobby, but I assume you get my point.