simple answer - cause it’s implemented to do so… I am fully aware, that for road bikes the use of cycle-ways is mandatory in Germany.
If you want 100% legal routing in Germany - simply use the bike profile - have said that, forcing cycleways is in many areas result in “none useful” routing like this one:
(Switch over to the road-bike profile to see the difference)
here is another example:
The big difference are the resulting TurnInstructions! (and that’s IMHO the most important reason why I use the service )
As a reasonable road bike cyclist (when I am on the bike) I am judging for each road individually IF I will use the regular street - or the cycle way (if present) - and while I am riding and approaching a turn instruction I can transfer quite simple a street-based turn instruction into a cycle-way instruction. I have attempted previously do this vise versa - but failed so many times! - actually that was the main motivation to join the openrouteservice development team…
Last example - see the turn instructions here:
and compare them with the road-bike version…
Please assuming that you are not able to watch the map while you ride - just listening to the turn instructions have to be sufficient to find the right way.