A speed limit isn't a target speed, you don't have to drive at 70 (or 30, 40, 50 or 60 where they are the limits) if you don't want though unless there's a good reason not to, why wouldn't you?
I've passed three advanced driving tests, driven on race circuits across Europe, have a car that's electronically restricted to 155mph. Even so I find there are times on a UK motorway when 70mph is too fast yet people drive at that speed because that's the maximum allowed - so they do it. Abolish the motorway speed limit and make people take responsibility for themselves (like they do in Germany).
Motorways aren't dangerous, they're the safest of all roads. Neither is speed dangerous, it's a contributory factor in a small percentage of road accidents. A lot of nonsense has been spouted about road safety in recent decades. The trouble is, if people hear it often enough they start to believe it.
'Night all....