Checking the IMDB table for the number of films released in 4K is now 63 in total. BestBuy has 541 different BD movies. It is likely to increase come the fall as more 4K televisions are purchased. Given there are 40,000 feature films in existence it seems that stores are not stocking them.
The ACE, MPAA and RIAA et alia like to sue illegal downloader but as fact checked, only 63 known to the IMDB and 541 at BestBuy mean there are no legal alternatives. This invites the response to these agencies to back down and reduce the cost which will go far to eliminating unlicensed copying. The most copied object was Windows 3.1 followed by Windows 98 and Windows 98SE. Microsoft introduced activation to reduce the unlicensed copying of their operating system. No movie or television show comes even close to the level of copying that Windows endured.
The original ATSC standard was developed in 1997 which has influenced production of media since. ATSC 3.0 includes 3840×2160 HRD10 and 4:4:4 chromaticity. In time this will bring UHD to cable TV systems as well as over the air broadcasts. Cable TV is slow to change at the best of times so the patent is likely to expire before any changes surface.
At present standard HD BD discs are the most common in catalogs. Television shows on DVD but are giving way to BD versions. Star Trek: The Next Generation was remastered for BD and the picture quality is astounding. The old Law & Order is available in a 20 season DVD box et. More recent television shows are available in FullHD BD.
The media rack has a few ancient DVD titles but most of the movies are BD. Until the selection of 4K titles improves the current selection of feature films is likely to be small. The focus has been more with television shows which offer at least some entertainment for the money.
Some movies like Indiana Jones, Star Trek etc are being sold as a 4K box set to achieve a slightly better average selling price. Even some recent TV shows are starting to surface in 4K box sets.
Movies have long been anamorphic due to the larger theaters built in the 1950s and 1960s. Some films like Ben Hur cost a lot to make but they earned a lot in theatres and subsequent television broadcasts. Several masterpieces were produced in the 1940 through the 1960s.
By the time 4K BD selection improves, the advent of 8K televisions will bring new demands for content. BD50 is fine for HD movies and H.265 allows 4K content. The more recent H.266 is intended to allow 8K content to be playable on existing BD media.
The LG 4K BD player does an amazing job of making television shows look good. Moving to an 8K television is still a few years away based on existing standards and technologies.