Eh, all of the "flying trucks" I knew about in the 70s had stall speeds higher than 75mph.
Not aware of the CH-37 Mojave, CH-47 Chinook (aka "flying banana"), HH-3 Jolly Green, nor SH-3 Sea King, eh? I was aware of three of those as a 7 YO before Star Wars came out... and had a Matchbox Chinook and Jolly Green. And saw Jolly's and Bananas flying in/out of EAFB & Ft. Richardson. No stall speed on a helo itself... tho', technically, the blades do.
Not that I don't appreciate the utility of doing 75 MPH over, well, anything, but that doesn't mean its not slow.
Compared to any current surface transport, 75mph (120km/h), is respectable; only the fastest trains go faster, and most don't make it that fast. It's also just fast enough that a bug can permanently blind if it hits the eye. And plenty fast enough to be a near-guaranteed kill if you hit a pedestrian. Or if you fall out.
Sure, the heavy helos go twice to thrice that... but the Air/Raft isn't a heavy helo. And many small transport aircraft have stall speeds in the mid 50's. DHC-2 Beaver 55 kts, DHC-3 58 kts IAS. The equivalent capacities of a passenger van and a large frame van/short lorrie. And the DHC-6 Twin Otter, 58 kts. capacity of 20 people plus luggage. Rode one to/from summer camp several years running. Rattles your bones so hard you never forget it. Beaver's cruise is only 110, and it's loiter speed (marked on the gauges of the CAP beavers I've piloted) was 70 Kts. Right about 75mph. That's the SAR op speed, too.
And we all know a Big Rig can hit 80 loaded... but they get squirrely in crosswinds. 65 was chosen as the national limit (only enforceable on federal funded roads, thanks to the courts) because it's the point where common speed crosswinds aren't going to flip a 40' box. (and yet, on Knik-Goose Bay Road, 2-3 a year flip from the morning and evening winds. I got a lot of sub-teaching days due to KGB Road being blocked by a flipped semi on a 45 MPH road...)
For the needs of the scouts or merchants for a grocery getter, SAR ops, and parts trolley, 75 mph is more than plenty. It's also much faster than a land-bound 4-ton crane... which it can also replace if the wind is low.