The 2000s decade was the heyday of physical media in North America and DVD was the dominant format. When it comes to Baby Boomers and Gen-X'ers reconnecting with the original Ultraman series, the vast majority of them have probably already done so with BCI's 2006 DVD sets or Mill Creek's 2009 or 2013 DVD reissues, all of which included the English dubs.
Heck, those Mill Creek DVDs are still available today for cheap prices! Like most dedicated kaiju fans, I would have preferred to have the English dubbing option on the BRD set, but for casual buyers who haven't thought about Ultraman in decades and want to reconnect with the English-dubbed Japanese superhero they watched as kids in syndication on lo-fi TV sets, Mill Creek's 4-disc complete series DVD set should do the trick.
Otherwise, the target demographic for these and Mill Creek's other upcoming BRD sets are folks like us, people who care enough about this stuff to post on message boards dedicated to kaiju and blu-rays and what not. Companies like Mill Creek or Arrow or Shout!Factory can generally count on folks like us to support physical media releases of niche titles that we care about. There's no reason to expect these shows to appeal to anyone who isn't actively interested in vintage Japanese sci-fi. No amount of advertising or classic English dubbing is going to make a difference there and that's okay. I appreciate Mill Creek for dealing directly with TPC to make these Ultra series available on BRD for folks like us.