Bleh. Most people just in too much of hurry. Going faster than any land bound creature alive for longer periods than any can sustain isn't sufficient. Must go even faster, because,
... not really sure what the because is, other than because. You don't save much time going 5-10 over speed limit (and the amount you save relatively becomes progressively smaller as you go faster), unless it's really low (20s, etc). Don't save much gas. Still moving faster and more comfortably than anything else on planet. But, no. Must go 5-10 over speed limit. Doesn't matter what speed limit is. 5-10 over, always, for almost everyone.
Frumple just doesn't understand. Go speed limit, maybe leave two-three minutes earlier at most. Get there at same time or near enough it doesn't matter. Don't break law in process. Why go faster when it doesn't make particular difference and is somewhat less safe? If in hurry, already late. Not point rushing then. Late is binary, more late still late.
Is side to most of that, but part of it for me, at least, is a sort of respect... m'grandfather did a lot of the road work in my area. I respect the expertise that went into that... if he and his fellows say "go 55", I say, "Okay. You're better at this than me, so I yield to wisdom."
'Course, I also know that almost all roads are capable of safely being traveled a good 20-30 over the posted limit -- they're built that way, at least most of the time -- but that's not the point. Point to me is that 'people I trust (in a roundabout way) says this is the safe speed' mixed with 'I'm not losing any meaningful amount of time not going faster'. Throw in a "it's more dangerous to be going faster" and it's just a no-brainer to me. Go speed limit, or slower. Only reason I don't just cruise at 10 under is because it causes vehicles to start building up and impatient assholes to start doing stupid-stupid shit like passing three cars in one go.
Now, one thing I will do (and have done) is pull right the fuck over if there's a crapton of tailgating whoresons piling up behind my law abiding ass. Just let th'bastards pass, I say. I'm not in a hurry, ever.