It would be nice if you could be able to take, or reject as many loads that will keep you profitable, and from a philosophical standpoint you can. From a reality standpoint, however, you can only do that if you have your own authority. When you lease on with a carrier, though, you are transferring the right to possession and/or use of goods or equipment (your truck) for a term in return for consideration. You and your truck become a tool for the carrier. If that tool becomes unreliable then the carrier will stop using it. It's really that simple. The carrier is there for carrier, not us.
If you are "forced" to take whatever they send your way, because you are at or below 67%, then you are forcing yourself to take it. They carrier is not forcing you to take it, as you can still turn it down. But it's a situation you got yourself into, by your own actions. There are exceptions, of course, but generally speaking when someone is below 67% it is because they are cherry picking, and have turned down loads that are profitable, it's just that they weren't primo loads with the kind of miles the O/O wants.
I'm usually in the 95% to 100% acceptance range, but I do turn down most of the loads that don't count as a refusal (more than 8 hours, more than 40% deadhead, etc). I turned down a load last week that was profitable for most people, including me. 12 miles deadhead, 187 miles, paid $1.07 per mile. It went from Dallas to Shreveport, but I had just spent the previous Friday-thru-Monday in Shreveport and finally got a load to Dallas. Then one from Houston to northeast Arkansas, and then one right back down to Dallas. I didn't want to go right back to Shreveport to end up sitting for a week or having to deadhead back to Dallas or up to Memphis or something, so I figured I'd wait it out for something better.
If I spend a lot of time in Midwest Hell my acceptance rate drops for the same kinds of reasons. A short load going to a place where there are 4 times as many vans as loads just so I can sit 2 or 3 days just to get another load going to an identical situation. No thanks, I'll pass.
The key is to know the rules of the game so you can use them to your advantage, to know when you should and should not turn down loads. You have to know how the acceptance is calculated. It's all of the previous calendar month plus the days of the current month.
Let's say it's the last week of June, so you acceptance is calculated using all of May plus all of the days so far in June. In May you had 12 load offers and you took 10 of them. So far in June you have had 11 load offers and you have turned down three of them. You're 18 of 23 in acceptance, for 78% acceptance. Another crappy load comes in and you turn it down, you drop to 75% acceptance, no big deal. Right? Wrong. Two days later you still haven't gotten another load offer and now it's July 1 and all of May drops off the backend, so now you have all of June and the one day in July. You are now 7 for 11 in acceptance for 64% and you just screwed yourself by turning down that last load (or one of the other three in June that were profitable, just not primo). If you'd have turned down three instead of 4 in June, you'd be sitting at 73% instead.
A load doesn't have to be at least 500 miles to be profitable. They trick is to keep your acceptance high enough so that you can be all cherry picky when you want to. I turned down a load to Shreveport, and got a 1300 mile load to Pompano Beach instead. I'd really hate to think that I had placed myself in a position where I HAD to take that load to Shreveport in order to remain above 67%.