Why would anyone not follow an RTA? Whether it works or not is quite frankly immaterial, it's a commercial request and unless you can't meet it for an operational reasons just do it.
The inference that 'people' ignore an RTA if it requires a slow down should actually be interpreted as 'a selfish Captain placing the other pilot(s) in a difficult position for no good reason.' I can't see an FO choosing to ignore an RTA if the Captains wants to follow it. With the roles reversed, how comfortable does the FO feel?
There has been a recent flurry of ridiculous and poor RT from our fellow company members that causes those in the flight deck to wince. If ATC are reading this, your frustrations are ours as well. An RTA makes zip difference to you I know, I have no idea if it works or not but the arrogance to ask a controller where the RTA traffic is defies belief.