Reverse importing, authoring is a right pain in the ass compared to DVD so the more ramshackle portions of the US industry don't want to bother, etc.
It costs around $1000-$1500 in licencing fees per BD disc, which for most home video releases is less than the lawyer would get paid to read the licence agreement, but for anime in the US is around 5% of projected GROSS due to low sales/bargain-basement prices. For shows that aren't dubbed, it's literally higher than all other production costs combined.
That's why the engsubs-on-Japanese-disc model works so well. Reverse importation isn't a problem when Aniplex or BV is getting $50 a disc either way, the BD fees are already rolled into the already-profitable Japanese release where they "cost" five or six guys' full-series purchases, and the core market buying them in the US is the guys who used to buy raws at the same prices so they're not too picky about the MSRP.