Essentially 80% of my betta tanks are uncycled. This is for various reasons such as extremely low pH (for my wilds), tank size and a lack of power sockets for filters and pumps to plug into.
While I think fish do better in a cycled environment due to its stable water chemistry, I have no issue with housing bettas in uncycled tanks. As long as appropriate
measures are taken to ensure there is never any trace of ammonia or nitrite present.
Also, I've had a betta swimming around while the ammonia was reading at 8ppm. He was acting perfectly normal and the only reason I checked was because I had noticed his caudal was showing some slight damage.
I do think everyone should own at least some form of water testing equipment. Bettas are extremely hardy fish, as evidenced by the conditions they are often kept in, and as I cannot gauge the quality of my water with my eyes alone, I prefer to have something there to give me that ability.