Sometimes an author can have mixed financial reasons for
using an alias/pseudonym.
1. If Stephen King wrote a romance, and it was good, people
would still not believe it. They'd look at the cover with its
buxom maiden and its pirate and say, "Pffft! Stephen King?
What does he know about romance? I bet the pirate tortures her
or goes insane or gets eaten by rats..." and they won't buy the book.
2. Most authors are not powerful, and they get trapped into a bad
contract with a cleverly worded option clause.
According to a book called "
How to be your own literary agent,"
an option is just supposed to be the publisher's right to guarantee
that he is the first one to consider the next manuscript from an author.
But there are plenty of ways that the author is trapped by it; if you
read the book you'll know why.
So one way to get out is to insist on an option clause that says
"This publisher shall have [the option] of my next book
written
under my own name, [Stephen King]..." and then
King has the legal right to submit another book, under another
name, to a new publisher without getting sued by his first publisher.