Drawback of hypermilling

[TruckHyperMiler]

I've been driving around 50-55 on the freeway for the past few months, managed to get my '83 diesel f-250 work truck from 15 up to 19.5mpg (this is with various loads of furniture, boxes, dirt, appliances, etc in the back)

Last night on my way home, going 50, some cars merged very slow, and instead of accelerating to pass them, I slowed even more to let them in, but they were going SO slow I just moved to the left instead.

As I accelerated gently back up to speed I noticed a cop behind me, and just as I put on my signal to move back to the right, he moved to the right without signaling.
So I stayed where I was, and waited for him to pass on the right, still not having accelerated up to speed yet.

After a couple seconds, instead of passing, he pulled back in behind me.

And lit up the red and blues.

After answering a bunch of questions (last thing I ate was ice cream, 2 strawberries, and 2 almond cookies, I am not under the care of a doctor or dentist) I did a balance test, and when I passed that, took my first ever breathalyzer.

In an area where everyone goes 75, why would anyone drive slow unless they were drunk?
I told him I drive slow in order to save gas (and I was going particularly slow while I waited for him to pass - I didn't point out that he hadn't used his turn signal).
He said that I was going 20 under the limit.
I wasn't sure how pointing out that the "limit" was a MAXIMUM limit, not a minimum, would be taken, so I was just mostly quiet and agreeable.

In the end, no ticket, but I can imagine getting pulled over frequently wasting a lot of time and getting rather annoying.