True. But some people will do everything (including ruining team morale) to play with their new shiny toy and it's usually easier to ruin that than taking steps for prevention. But you are generally right.
>But some people will do everything (including ruining team morale) to play with their new shiny toy
Because everyone has different interest/goal. The interest/goal of junior developer is different than the senior developer, even though both working in the same company.
It might very well be in their best interest for the junior develop to play with shiny toy, if that the case then that is what they should do.
While for the senior developer though it might be in their best interest to prevent that.
If a team's management can't prevent this from happening, then they've got bigger problems to worry about.