Some hotels charge for late checkout too -- though maybe that's more theoretical than actual (for HHonors members, esp. Diamond/Gold, I think you could make a case for waiving it if they tried to enforce it).

Anyhow, would you have preferred that they flat-out deny the possibility of early checkin? It seems that a lot of hotels do that -- they don't necessarily check availability, or they don't even consider trying to accommodate you in some fashion. Instead, they just state categorically: "checkin is at 3 PM." I would actually condemn that behavior a lot more than I would condemn a charge for early checkin. If I were offered an early checkin for a smallish fee, I might consider paying it! Though first, I might ask if the fee could be waived.