Having the proper cheek weld is important and making sure that its the same shot after shot is critical to fine accuracy. The adjustable cheek piece is a great adition if you like scope with obj lens over 40mm as with most folk with most guns you will start to rasie your head up off the stock "breaking the cheek weld" and you head placement will not be consistant nor will the pressure that your putting opn the stock.
With tactical rifles I find it VERY important to be as comfortable as possible while behind the gun as you might have to be their for hrs on end and you need to be focused completly on what your looking at through your scope , about 95% of a police snipers job is relaying info back to the command and entry team , in alot of cases you maybe the only eyes they have.
If you ever notice the military sniper rifles almost all of them have somthing duck taped to the stock , thats foam that they have taylored to fit the gun to them.
You don't see to many Bench Rest shooters with adjustable cheek pieces but in their case I think they try to have as little contact as possible with the gun , but in just about all other shooting sports for clays to Palma the shooters either have stocks built to fit them or adjustable cheek rest.