You mean northbridge? There's the overclocking arms race as well as an increased focus on aesthetics. There's also a growing number of features on boards that you wouldn't have seen a few years ago. The debug LED on the Asus boards is a prime example, or the shielded onboard sound on the G1 and RoG series.
Ultimately though, they know that just about anyone with SB, SB-E, and Ivy are looking to overclock with how insanely simple it is. The capacitors, VRM, and phase management all need to be decent quality to handle that.
If you want a motherboard that isn't designed for any of that, there is always stuff like cheap H67s to get the job done. It's silly to look at high end stuff and say "why are high end boards expensive when there isn't a northbridge anymore?". Northbridge is only a small portion of what a motherboard does.
The problem is that these aren't the high end boards in this price range. You're looking at 350-400$ for a high end board now. Debug displays are about as new as the combustion engine. Motherboards from the 80's had them. And having onboard sound that doesn't sound like it's running through a shitty FM transmitter is hardly an advanced feature. H77 doesn't support overclocking, and Z75 boards basically do not exist. Z77 is really the only choice for people who are not looking for a 'mom and pop' machine. My 775 motherboard was in the <$100 range. Similar spec'd boards now seem nearly double in price. Hopefully we just need some time to get some reasonable Z75 boards out.