Really? There really are cyclists who absolutely want other cyclists (who might not be riding fast road bikes) to cycle on 45mph roads, with leftover car part debris from previous car accidents on that road, surrounded by several lanes of fast-moving vehicles (where motorists would definitely be unhappy, having only one full lane and honking at the cyclist, to tell them to get on the sidewalk) who will pass inches from them and won't give the cyclist enough room to avoid the potholes on the road--even though the sidewalk on those streets might be cleaner, safer and without pedestrians? Where there are blind curves with hills, and a risk of a fast driver--who definitely won't expect to see a cyclist in their lane--crashing into the cyclist from behind?

Sometimes, it's difficult for a cyclist to make the light, while cycling on the road, especially when, even though they're in front, drivers like to quickly move in front of them because the cyclist is slower, and they don't want to be stuck behind the cyclist. And, when a cyclist has their high gears because they were attempting to cycle faster to try to make the turn light, but the light doesn't last long and changes quickly to yellow, maybe the cyclist doesn't want to have to try to pedal in the highest gear, once the light turns green because it'll be slower and harder to pedal to make the light in time (and motorists behind the cyclist wouldn't be happy if they wouldn't be able to make the light, due to the cyclist being slower).

So, yeah, maybe the cyclist felt it would be better to use the crosswalk this one time, where there aren't any pedestrians that are ever there, using it. Not every place is crowded like the Northeast, New York area, etc., or has tons of pedestrians that use sidewalks; some places around the country don't have any pedestrians, or maybe one or two that use sidewalks in that area. So, cyclists aren't being a danger or a nuisance to pedestrians, when there aren't any there, in the first place.

So, that's why motorists and some cyclists might feel it's okay to use the sidewalks: no one else is using them, and motorists feel it'd be better for cyclists to be out of their way, on busy roads. Some cyclists might be tired of experiencing motorists honking or shouting at them, while they're cycling on the road; so, cycling on the sidewalk, sometimes, might also bring them a little more peace and a nice break from that.

Plus, not everyone rides a road bike that can keep up with fast traffic.