What kind of hardware are you developing and where does your 'hardware' currently reside, on your computer? I'm not quite sure what you're missing about the whole concept of an FPGA. Don't you have any interest on interfacing with it on a physical level in the real world?
Most of the time people create HDL code for the sole purpose of putting it on an FPGA and using it in the real world. Take a car for instance. You don't drive around in CAD models and mechanical simulations do you? When you buy a TV - in place of the digital electronics would you rather get a bunch of VCS simulations and binary files, OR.. the (application-specific) FPGAs?
So I would say the benefit to having an FPGA is that you actually get to use what you've made in the real world, unless you're content with creating things in a vortex somewhere.
Edited: I see you said "added" benefit. If you owned an FPGA, you would find out that designs sometimes don't work in the real world as they do simulations and for extremely "interesting" reasons. There are multiple issues that can arise like: problems communicating with a peripheral IC, metastability, voltage levels, timing, propagation delays, reset anomalies ..etc., all resulting in tons of head scratching. Hey, think you're finished with your design!? Nope! Someone found a way to break it! Or better yet.. they got the 1 (out of 1000) that uncovered an intermittent issue!