Buyers expect to get a fully functional player, and the front panel only has the basic controls on it. The remote gives full access to all the functionality, including such things as programming it to control other devices (e.g. TV or amplifier). As you have already found, they're not expensive.
Check the manual to find the exact part number of its remote (i.e. don't buy a generic replacement), get it, and test the player to be sure that everything's working as it should.
One other note: try to buy a New Old Stock replacement remote rather than someone's visibly used one if possible, because the most frequently used buttons (e.g. Power, Play, Stop, Pause) can start to wear and go flaky after long periods of use.
