We have plenty around here. Luckily, timber rattlesnakes typically give lots of warning, and are not particularly aggressive. But, like any animal, temperaments vary, and in areas where they are common, you don’t want to be wandering around in shorts and hiking shoes...
I live in the Driftless region of Wisconsin. This area is very hilly with lots of rocks. According to one nationally known snake expert I talked to one time at a nature meeting, it's one of the best places in the U.S. for timber rattlesnakes.
Yet growing up in the area and climbing the bluffs regularly as a child, I never saw ONE timber rattlesnake. Or any rattlesnake. Because, as you stated, they, timber rattlesnakes, are not very aggressive. There has not been one single reported death from a bite from a timber rattler in this area.
In fact, there has only been on reported death from rattlesnake bite in Wisconsin history. Some young girl actually sat on a rattlesnake in eastern Wisconsin some years ago. She was too far from the hospital and died from the bite.
In fact, the only rattlesnake I've come across in my sixty+ years of hiking in the area was very dead. So it's not a real danger to hike in shorts and sneakers. Just be careful where you put your hands when climbing on or around rocky bluffs, and if you hear something rattle, back away.