It is ideal to have the ground and neutral separated, yes. Safer, definitely, but obviously they work ok with the 3 wire system. The reason it is better to have the separate is with a 3 wire system you use the ground as the neutral. There are some things on a dryer that are actually 120V..i.e. the light, backlighting for the buttons or selections, and the timer. When these operate there is a small amount of current on that ground conductor, which is also connected to the metal of the appliance. That being said there are certain circumstances where any bare metal you touch would have current present. It usually is not enough or people aren't grounded when they come into contact with it but it is possible. With the 4 wire system you eliminate this chance. I hope I explained this clearly and by no means am I trying to scare you into anything, just trying to clarify why the code was changed. This is the same reason the jumper should be removed when a new unit is installed. There are literally millions running everyday with either a 3 wire system or with the jumper intact so it is obviously not an imminent threat. Maybe have it done the next time you have a reason for an electrician? Truth be told connecting in the panel isn't brain surgery either. You could shut off the power and do it yourself safely. If you want to go this route feel free to pm me and I can walk you through it without an issue.