Pro cycling is already a pretty dangerous sport, both on track and on the road. To mitigate those dangers a very important part is having a maneuverable bike. Recumbents are nothing of the sort.

I doubt that any pro-cyclist wants the speed advantages of one if it means that cornering is more difficult, veering into dangerous.

There are also clear safety advantages to recumbents, like harder breaking without flipping over and an unobstructed view without sacrificing aerodynamics, so I do not think they should automatically be considered less safe.

I am also pretty confident that the 'manoeuvrability' disadvantage is completely irrelevant for any individual track event. And do you think that it would be an important factor for time trials?

It depends but I don't think a recumbent bike is all that great when climbing or descending. I can't see cyclists wanting a recumbent if there are any significant elevation changes on the course.

Recumbents are beasts of descending. As long as there are no turns. On a straight descent, they'll beat anything without even trying.

We are talking about pro-cycling. The descents in pro tours have _a lot_ of turns.

Flipping over because of hard braking is not something that happens in pro-cycling.

[edit] And yes, for time trials recumbents would be nice, but already time-trial bikes are pretty different and unsafe, I don't think the UCI would allow even more risk.

The view from a recumbent bike becomes highly obstructed when you're riding in a tight peleton. The group road rides that I do don't allow recumbents for safety reasons. Traditional bikes have their dangers but at least your eyes are up higher to allow a good view around other riders.

Maneuverability is important for time trials. Most courses have several tight turns and crashes are common.

The rules are in place not to hold back speed, but to protect the image of cycling. A recumbent may be faster but it does not look like a bicycle to the average person and changes the image of the sport.

Things like better shifters, lighter frames (within reason) more aero parts (within reason) are still allowed.

> lighter frames (within reason)

The UCI's 6.8kg weight limit is much higher than what is achievable with modern materials. So much so that there are frame builders who can build you an "illegal" bike made out of _steel_: https://www.rodbikes.com/catalog/outlaw/outlaw-main.html

They do drop the limits over time. The reasoning is they want everyone to have very structurally sound bikes for safety. You _could_ build an ultra light steel bike but it might fail and cause serious injury.

With a minimum limit, no one feels the need to make their bikes less than perfectly strong. And when every OEM is making frames at perfect strength under the limit, they drop it.

They haven't ever dropped the limit - a weight limit was introduced in 2000 and hasn't changed since: https://cyclingtips.com/2013/08/the-6-8kg-limit/

Could also put an engine in there. Sports are defined by arbitrary rules.

There are actually sanctioned eMTB races now. Seems a bit lame but whatever.

Why is that lame? Because they have a machine helping them? Is motocross lame?

Even something like a small faring, like the little plastic windshield on a motorbike should increase speed. One concern though, is that it would mitigate the advantage of drafting and totally change the strategy of cycling as it exists today (eg. re. the pelotón and breakaways).