It's not a motorbike two people can sit on; although a more powerful motorcycle with a sidecar attachment would be very cool. (I assume this could probably fit 3 people.)
You express concerns with rarity, it's possible this is due to the smaller size of the map compared to the new nasdara map. I think that if this is the only reason the Devs are not making bikes more common on chernarus and livonia when the update moves to stable, they should reconsider.
I would take an auto run ability instead, (I have novel ideas on how this could be implemented to be a simple + fun mechanic.)
If it has to do with economy and server performance, I have an idea that can keep entities lower, and I was saving it to make a mod myself, but it's a good idea so I'll share it in hopes that someone makes use of it because I can't until the tools work in my environment:
Remove all car entity spawns
Add an ability to interact with static car wrecks
This creates an inventory slot for the car
Add parts that need repaired and get your car to working order
When the repairs are complete the asset is deleted and an entity is spawned in its place
This is better than the current system because:
It keeps entities lower, hypothetically improving performance
Cars are spawned as the economy wants them, not as the defaults dictate
Economy can still be controlled by the spawning of repair parts, based on active entities
Cars now become abundant, and fixing a car is more of a rewarding minigame than an endless gamble
Further features:
You could even make the repairs an engaging minigame of timed inputs and accuracy, press the interact key to begin, press it again, or hold right click to cancel, maybe also movement keys can cancel, but then while in this repair mode, make a selection of keys give input to the minigame. Even something simple would be super cool and completely change the atmosphere of the game, giving players more to do, and letting people get into a run with more time for exploring the parts of the map they want to explore at a given time.
It doesn't have to be bad for new players either, it doesn't need to detract from the gritty scarcity (is it really lore friendly to have such scarcity? this is the first day of the outbreak afterall). I remember when someone showed me how to make a fire, and they showed me how to make a hand drill kit. I didn't know that was possible, I never saw a fire before, (I only had a few hours in the game at this point I think,) but I remember the magic I felt when I saw that, because I felt like anything was possible in this game, and I felt the power from my new learned skill. He didn't really think much of it; but after he left, I built a fire when his eventually went out. This is from building a fire. I imagine you can take my idea and interpret it in a way that captures that same magic for new players in the future.
I'm getting excited talking about this feature actually, because it's something that would be simple to implement and it's a feature that I've been thinking about for some time. If you would like to see this feature become a reality, and the Dev's don't do it better first, show your support by liking this comment, that you would like to see the DayZ tools stable on non-windows computers.
This change to cars is something that would make a "broke man feel rich", and that may be something DayZ could use.