“Kind sir, you are out of compliance with article 1.3.013”
A recent Cyclingnews report from the Tour de France prologue highlighted the enforcement of an equipment rule, sending some teams scrambling doing last minute modifications and replacements to stay in compliance (ref link). The spirit of UCI equipment rules is to maintain an even playing field (this is big business after all) and rider safety (no positions or equipment that endanger riders). Both debatable points, as riders will push the limits of their equipment, no matter what they are allowed to ride.
Of note in the enforcement of equipment rules during the prologue was that only saddles with integrated friction pieces were permitted, and others with post manufacture modifications had to be changed. Prologo has a saddle, the Nago EVO TTR (http://www.prologotouch.com/nago_evo_ttr_nack.php) that has integrated ribs, helping the rider to “sneak up” on the saddle without falling off. You could modify your favourite saddle (and triathletes should consider doing this), but not in a UCI race. But why sneak up?
Rider position is key to power and aerodynamics. By now just about everyone is familiar with Dan Empfield’s slowtwtich fitting protocol (Here). In summary, it is about ideal muscle activation and ideal aerodynamics while still maintaining control of the bike, all within the confines of the contact points of a two wheeled double diamond bike. And for the record I whole heartedly agree with the axioms, as do most of the fitting protocols out there, regardless of who is teaching them. Of relevance to this discussion are that steep and forward are better (saddle angle, saddle height, position over the bottom bracket). For triathletes not governed by UCI rules, it is anything goes; you can pick the bike and set up that allows you to most easily get into the best position. For UCI governed athletes (road racers and draft legal tri/duathletes), there are rules that govern just how you can set up your bike, and that impact your position on the bike.
Read to your eyes bleed here, but summarizing two of the most pertinent points, your saddle has to be 5cm behind the bottom bracket axle and your bar extensions can extend no further than 75 cm forward of the bottom bracket, with some allowance made for tall or gangly riders. The rules have the bike positioned back, but the rider wants to be steep. And so they do all that they can to achieve this. A saddle with grip allows you to move forward and not fall off. Forward on the saddle can sometimes also facilitate low in the cockpit, which can be good for aerodynamics and perhaps for mechanical advantage.
What is a normal person to do? If you ride UCI time trials or draft legal triathlons and duathlons, have your bike set up and fit checked with the rules in mind. Get used to the position, get used to asking for an exemption, get used to being uncomfortable and use anything permitted to ride in that ideal position. For triathletes, as I said, just about anything goes.