Reprinting cards/sets not offered to arena

WOTC had designed sets just for commander. Dr. Who for example. These were only print products, not for arena. Arena has brawl commander like play why didn’t they offer these sets in arena (digital).

Would WOTC revisit these UB type sets and with new contracts offer it digitally, or bring a more expanded version to standard? I’m a fan of dr who and would be nice to play them on arena.