When I was last monitoring the ham bands' SSB sections (I stopped about four years ago), I don't know if I was encountering 'dirty' transmitters but yeah, a lot of the guys push the power when they don't really need to -- especially during contests. CW not so much...
On some of the ham forums, there have been suspicions mentioned of guys using more power than legal during such contests. Whether that's true or not, I have no way of knowing, but ever since I've monitored the ham bands, I've encountered lots of ham stations that splatter 10 khz to either side of a target frequency. I just counted it up to my receivers.
And, ironically, if another ham gets on the channel and complains about a splatter master, the inevitable retort is "get a better radio, old man!"