I think the following is a possible problem. Let's say there was no magical healing whatsoever in the game. Then you'd have this "weakest link" problem, in that whoever got beat down first would trigger the end of the adventuring day. Player A: (on death's door) "Man, we have to get out!". Players B-E (who are relatively fine) "Grumble, grumble, I guess so."
With 1E-3E clerics & curing items, healing is a party-wide resource. If one person takes some unlucky shots, they get more healing, and the party keeps going. It promotes teamwork & cohesiveness. Everyone's tracking that resource and helping the overall party to stay in fighting shape. Only when all the communal healing is gone does the party as a group retreat.
With 4E "healing surges" you're back in the first situation, where healing is siloed to each individual. One person will take more damage over a few encounters, and that will trigger a party retreat, even if everyone else is fine. There will be a bit of a disconnect because Players B-E will be feeling heroic and brave but they have to turn tail because one person burned up all their healing surges. Most people's healing surges will not get used in any adventuring day.