If you want sparks there plenty here just read the technical page... O wait you ment on the trains well dtg can't do everything right away you know...give it time.
The thing is that IMHO, sparks would mainly appeal to the serious “simulator” players who want accuracy rather than the casual “game” players. However to be a serious simulator driver, one probably needs to stay in the cab and not use external camera views (immersion and all that) so they would not see the sparks anyway. Just a thought and happy to be corrected.
I think they could also appeal to the "I want an inexpensive but detailed model railway set" types too.