Bushings? You mean the bellows covering the top half of the strut?
Example pick from Tirerack - one is of the strut mount (make sure yours is in good shape - should have some clean grease in it), the other is the strut boot.
The dust boot protects the strut shaft (piston rod) from dust and moisture. Not a 100% seal - but better than getting also sorts of stuff on your struts. If you only want the struts to last a year or less - then don't bother getting new boots. If you want to hold up for a good period of time - protect them.
Some have a built in bumpstop (OEM KYB are that way) - if the boot (bellows) are torn up or dry rotted, the bumpstops are probably toast as well. Your struts should have come with new bumpstops - but also depends on the manufacturer and where you got them.