Are my turn signals invisible?

After returning from a trip (And noticed going to) that more often than not cars will completely ignore my turn signal when I am in my MH. The typical scenario is being in the right lane on the interstate, coming up to a slower vehicle, wanting to pass so I signal to get into the left lane. Even cars that are beyond the rear of my toad will not only not allow me to come over, they actually speed up and then seem like they take forever to pass me, meanwhile more cars ignoring my signal and doing the same thing, just rolling up beside me. I checked my lights, they all work. It's happened in other scenarios but I am finding more and more people are totally inconsiderate of other vehicles and have no regard for letting larger vehicles over, or any clue about stopping distance and cut you off. And it goes beyond that, cars will actually speed up to keep you from getting over in front of them. I guess they feel that whatever destination they are going, being behind an RV for 30 seconds is unacceptable. I know it's not right but I found myself a few times that when I know I am clear, despite them speeding up after seeing my signal, I come over anyway, and take my time. 2 wrongs....

And what's up with cars not letting you pass them? Coming up on a car going 62 ish (I know cuz I look) getting in the left lane to pass, and they speed up. At one point I was doing 72 trying to pass the same car and not making any headway (they obviously sped up to the same MPH). I had to give up, fall in behind again and they slow back down to 62 again. What's that all about? They aren't looking at me so I don't think it's malicious. I don't get it.