Just because you are smart enough to check your blind spot doesn’t mean everyone else will.
The number of drivers who change lanes without looking properly is staggering, so put the onus on yourself to stay out of trouble.
If you notice you are cruising along to the right of and slightly behind another car, there’s a good chance they can’t see you. Either accelerate to pull alongside or in front of them or drop back until you’re sure you can be seen in their mirrors. Take extra care around trucks and large vehicles as they have bigger blind spots and slower reaction times.