If your players are focusing only on strikers, they are completely and totally overlooking how essential the controllers, leaders, and defenders are to allowing those strikers to shine.
4e is a team game. Strikers may be your star running backs, but it shows a lack of insight to think their contributions are more significant than the offensive line's.
Although what you say is true, people are people.
They enjoy what they enjoy.
I have told my players to play what they want to play. The only required role ime is a leader because healing is the main advantage that PCs have over NPCs, so if the players do not take a leader, I will use the DMG guidelines to supply one.
Our current group has:
Human Semi-lazy Warlord
Elven Thief
Dwarven Hybrid Fighter|Barbarian
Human Scout
Human Hunter
Eladrin Bladesinger
Dwarven Slayer
For all intents and purposes, the Warlord is (mostly) a striker because she gives extra attacks to the other strikers, the Thief is a striker, the Fighter|Barbarian is a striker, the Scout is a striker, the Hunter is a partial striker (shooting against the same foe with a group of melee strikers with Aspect of the Pack Wolf), the Bladesinger is a partial striker (2 rounds of Bladesong plus bladespell power), and the Slayer is a striker.
Every player arranged for his or her PC to do striker level damage, at least part of the time.
So, it seems like our group is 2 controllers, a defender|striker, a leader, and 3 strikers, but our group of players has decided that the ultimate form of control is death. A dead foe (typically) doesn't fight back.
The group doesn't (typically) need a lot of healing because it wipes foes out so quickly that the foes don't get enough attacks to force the group to heal (course, last week, I threw an N+4 encounter at them where they took damage if they did damage and it really threw them for a loop

).