Why is there no sealant?
You can use inserts that make rolling a tyre off less likely. It's not usually a problem in itself though (on the road), it mostly only happens after a puncture, when the tyre has lost pressure.
The sealant must be all over the road.
I've seen those inserts. For you and I they make sense, for pro's, not going to be adding any weight to their bikes, are they.
I've just spent an hour wrestling with those 28mm tyres. I packed in the end and opened a new pair of 32 mm tyres. I've just ordered a new pair too. As big as 28mm looked, to my old 19mm riding eyes, they're nowhere as good as rolling on the 32's. My tourer didn't have 32mm tyres back then. I love all the tech advances that have happened since the mid 70's on. Clothing, frames wheels, groupsets, everything.