This is a subject we tend to get around to from time to time on the forum. Let's not pretend that nobody has ever tried to make 8ball the standard game in pro pool.
In 2006, Kevin Trudeau's IPT 8ball tour offered more prize money than any pool tour in history but his business model fell apart. About 10 years later, Darren Appleton created an impressive new tour called the "World Pool Series" which played 8ball. In the end, however, he could not make financial ends meet and the project lasted just a couple of years. No, we have the Ultimate Pool events trying to bring 8ball back to prominence. Nobody has made a really big splash with an 8ball tour yet, but the day may be coming.
A major reason that straight pool was replaced by 9ball (approximately 1983) was that it was too slow to make for good viewing. The worst thing about straight pool was the calling of shots. The player would call the shot, wait for the referee to repeat the call (which only a few of the attending fans could hear) and then shoot. Fans grew weary of call shot, and it was obvious that televised pool would do better without it.
Snooker, which was starting to gain some momentum at that point, had it right. You never had to say which red you were trying to pocket or which pocket. If you made a legal hit on any red, then any red that dropped counted. 9ball was the same, for on any legal hit, anything that dropped counted. TV viewing always worked best without call shot.
When TV coverage became accessible to pro pool, they knew they had to play a game that would move along at a much faster clip than straight pool. As so many of the best pro players were already playing 9ball exclusively (examples include Earl Strickland, Jose Parica, and Buddy Hall), the choice, right or wrong, was easy.
Hence, the undeniably intuitive argument for 8ball being the pro game has not held up very well in practice. That's because recreational players, on average, so rarely watch the pros. Most of those who follow the pros are more serious players, and most of them would rather watch 9ball.