I have a 12 foot wide MUP in perfect groomed condition all the way from my house to my job. I never deal with a car. I never have to stop. There is never another person on it. I can make twice the time on the MUP as I can on the street, which is saturated with stops, potholes and cars. Do you have anymore answers for the masses?
Chill.
Around here, most of the best intercity routes are MUPs. Head down any of them at rush hour and the number of riders you'd see is like halfway through a TT race.