Why not, though? The differences between silver and plat are mostly mechanics, decision-making, map awareness and objective control.
Correct me if I'm wrong, but generally stealing kills is bad in several situations:
-You're the support. This is situational - there are situations where getting a kill or even first blood on a support gives you enough utility and vision which can lead to buff steals, kills, and ganks.
- You're the jungler and your lanes are struggling. In this case though, even stealing the kills still allows your teammates to farm and denies the enemies, so it's not fatal, even if it's not preferable.
- A majority of your team's kills are concentrated on you. I agree, this is the least preferable situation, but unless a player experiences this for themselves it's hard to explain how bad it can be. However Darius, Katarina, Kha'Zix and others with resets are one of the ideal candidates for "I have ALL the kills", since if they get that one kill it can start a nice chain reaction, and in general it's a lot easier to carry low-level games.
I honestly can't think of any other situation.
A new player should be learning first that League is about objectives, not kills, then how to best capitalize on kills [when to take an objective, when to push the wave, etc], and last the details of kill distribution. For a new player a kill is a kill and the beneficial effect is there no matter who got it.
edit : Virex, dude, are you telling me you would like to prevent new players from experiencing the joys of MANDROPPING every single fight, every single time, all the time? Because if so...
reedit : If you teach new players to call lanes, remember to teach them not to be surprised when they start playing ranked and every single person they end up in a lobby with them immediately starts trolling them, and certainly not without a reason.