why does Jerome hate steam launches?what problem did they have with steam launches?

Jerome hates being signaled by the launch to get out of the way. The only problems they had with the steam launches were problems they puposely caused on their own.

There is a blatant bumptiousness about a steam launch that has the knack of rousing every evil instinct in my nature, and I yearn for the good old days, when you could go about and tell people what you thought of them with a hatchet and a bow and arrows. The expression on the face of the man who, with his hands in his pockets, stands by the stern, smoking a cigar, is sufficient to excuse a breach of the peace by itself; and the lordly whistle for you to get out of the way would, I am confident, ensure a verdict of “justifiable homicide” from any jury of river men.