Currently there is only a negligible difference between level 7 and level 10 alpha chests. The rewards aren’t enough to make players want to advance. In fact, many choose to fight lower alphas in order to get keys faster. This gives them more rewards than fighting higher level alphas as they place higher.
Previously I’ve suggested increased premium token odds (1 in over 6 months is way too low) or a chance at 3* scales. I think putting these chances in a 10* alpha chest would draw many people to wanting to fight 10* alphas