Because there aren't any RTX cards available at the lower MSRP and there won't be in the coming months either. Just like how AMD's Vega was actually decent at it's MSRP, but it was impossible to buy at MSRP prices until around now, a year after release. MSRP is just a number, we care about reality. Maybe some models will start hitting MSRP pricing some time from now but that doesn't mean anything right now.
Also, Nvidia has made 2 device ID's per card for this generation. One of them is for the FE cards and other factory OC'ed AIB cards, the other doesn't allow factory OC'ed cards and is most likely the one that's going to be used for cards aimed at the lower MSRP. That also obviously means worse binned chips and cheaper coolers so those cards won't be as fast as the higher priced ones.
We don't know the real performance of the 2070 yet. 2070 will be ~600$ at launch where as a 1080 is currently ~450$
Again, a 2080 is currently ~800$ and a 1080TI is ~650$
And again, a 2080TI is currently ~1200$
Which don't actually work in anything yet and we don't know what the performance will be like.
Look. I get your point but you're doing yourself a disservice by comparing MSRP to MSRP when neither number reflects reality. Maybe some months from now the situation will change and then we can re-evaluate thing but that's then and now is now.