To be honest I only have 2 BB reviews here. Make it sound like I have been raw dogging a whole village 
I get tested regularly and I've never had any STIs in my life. BB is arguably not even too risky if both people have clean results. There are lots of young girls nowadays that will have raw sex with random strangers without checking any results which is more reckless.
Clean test results don't eliminate all risks from unprotected sex. There are important factors you're overlooking.
STI tests can't detect recent infections due to window periods. HIV may not show for up to 3 months, whilst other STIs like syphilis, hepatitis, and herpes have their own window periods. Someone could test negative whilst actually being infectious.
Unless contraception is being used or pregnancy is desired, this remains a significant consideration that "clean results" don't address. Standard STI panels also don't test for everything, HPV (which can cause cancer) and herpes often aren't included. Many people with herpes are asymptomatic and unaware they have it.
You're also relying on partners being honest about their testing, their activities since testing, and their interpretation of "clean" results. Testing is only a snapshot of status at that moment, not a guarantee going forward.
Comparing yourself favourably to others who may be reckless doesn't make your own risks disappear. Safer sex practices exist for good reason, even between tested partners.