Because "great" 26 year olds cost twice as much money...
Id say having a core of English players is usually a good foundation for a squad.
Also, they are more likely to come in and hit the ground running as theyve got league experience whereas with overseas players they may not adapt to the league or country.
You've been bleating on for ages about spending 30-35m on Aarons. How many rightbacks are going for double that? It's more that if someone is over 25 you call them an oaf and if they're under 22 you're reapplying the lipstick on your sock puppet.