The rear "set" trigger is usually fairly heavy in pull.
Its sole purpose is to "set the kicker" on the front trigger, so that it will have an exceptionally crisp, featherweight pull, measured in the ounces. If you don't use the rear trigger to "set the kicker", then the front trigger will have a pull weight more in line with those rifles having a single trigger, around 2-3 pounds. (Unless they're single-set triggers, like Canjar, Kepplinger, etc)
One can still find the double-set trigger assemblies for installation in '98 Mauser actions. I believe there are one or two on e-Bay right now. The double-set trigger is considered a classic installation for a fine sporting arm, and do nothing to hurt the price of the rifle. I'm quite partial to them, and have a double-set trigger arrangement on my 1874 Sharps Business Rifle. I will also install the Mauser double-set trigger system on my .45-70 Siamese Mauser Express Rifle project.