Is there a rule against it, is it bad taste, or are people too proud to use one?
5. Jumping
Players may use jump shots in One Pocket as long as they are performed with the player's own standard playing cue using legal jumping techniques as defined in General Rules. Specialized jump cues are not permitted in One Pocket.
Please note that many players, poolrooms and tournament directors have differing opinions on specialized jump cues. It is recommended that players check with their opponent, the 'house man' or the tournament director prior to an important match to come to agreement on whether specialized jump cues shall be permitted or not.
hmmm... lol
In other words, WPA rules say no, and anything else is subject to change via an agreement between players or TD's.
You wanted to know if it's in bad taste? Yes, it is.
If Jimmy Bob from Wannabe Hustler City came over and decided to use his new J&J Jump cue after I played a 3 rail safe, he'd get the back of my hand across his face.
Lol Thank you Dave, I like that answer much better