From when I first had a half good bike (back in the medieval period) I had cyclometers, and wouldn't be without distance measurement. I record distance to help me monitor my exercise effort and also to help control and monitor bike maintenance.
In recent years I've used so-called bike computers. Still get the distance but get speed as well. Occasionally it's interesting, but it can be a distraction, and as my riding now is either functional (transport) or exercise and leisure I don't have much use for knowing speed! I'm either interested in getting where I'm going, or enjoying where I am and what I'm doing. Much more important than speed.
A speedo would have been useful 40 years ago when I did TTs, but just wasn't available. Didn't worry us much though.