First, the delta configuration is inherently unstable. If the trike gets any kind of side force at speed it becomes very difficult and unnatural to control and recover. In almost all cases when a delta trike loses control at speed it will flip and roll. You may be aware that 3 wheel ATVs have been illegal to sell since the 80's for this same reason.

Also, delta trikes (at least the ones on the market currently) cant lean, so the rider has no control over center of gravity, which is generally pretty disastrous in any kind of emergency control scenario on a motorcycle.

What is particularly egregious is that they are specifically marketed and sold to older people who no longer have the strength or dexterity to control a regular motorcycle. They also usually have a lifetime of muscle memory from 2 wheel bikes that does not apply and often actively hurts their ability to control a trike.

The only way to buy insurance on them is through a specific carrier that is essentially underwritten by Harley Davidson. Death benefits are capped at like $30k.

Tadpole trikes like Can Am makes are fantastically safer, especially since the forward wheels camber and the trike can lean; however the comment about old people who have no business continuing to ride a motorcycle still stands as this is still the market segment they target.

From what I understand they are less stable than two in the front and one in the back.

Motorcycles lean to turn at speed, the trikes generally can't and are prone to tipping or flipping.

I've only ever seen them in low speed parades though.

Not sure how the slingshots with two wheels in front and one in back are at speed, i generally only see those at low speeds in cities blasting music instead of trying to get anywhere.

iirc they tip over a lot more easier