While I understand your point is likely that sidewalks would come before later advancements (like support for bikes) I want to make it clear that bikes do not belong on sidewalks.
If you ride a bike please ride it in the street with other vehicles. This is the law in some jurisdictions (such as where I live) but frequently ignored.
Failure to do this poses a serious risk to pedestrians. Please do not use sidewalks as an alternative road.
I've stopped advising people to not ride bikes on sidewalks, especially opposite the direction of traffic, even in situations where it's legally permitted (for example, kids in my area are allowed to ride on sidewalks).
People get really worked up when you ask them to stop, really angry! Which I find so odd because if somebody comes up to me and says something is both illegal and unsafe, I check the laws, and put some critical thought into what the risks could be, and then typically comply if I'm convinced, or simply respond with "I have heard what you are asking, but it's not absolutely required, so I will continue to do so."
If you ride a bike please ride it in the street with other vehicles. This is the law in some jurisdictions (such as where I live) but frequently ignored.
Failure to do this poses a serious risk to pedestrians. Please do not use sidewalks as an alternative road.