On the contrary, Mahrez is a talented aging veteran who knows the system and will be more comfortable with a diminishing role as he gets older. Gabby and Sterling are entering or in the middle of their peak years, it makes sense that they are both less amenable to diminishing roles.
And for the record, the policy hasn't changed at all. We sign young talented players from other clubs to compete and possibly beat out guys already on the team. Then we re-sign those who 1) make it and 2) want to stay.
Gabby and Sterling fail element #2.