I once used my favourite Darcy quote "I would by no means suspend any pleasure of yours” to end an uncivil conversation. I don’t think the person understood at all, but it made me feel good!
I always thought he was sincere when he said that. Sort of like flirting. He was angry at the time, but not at Lizzy.
(And Austen also implies that being a governess is an unsavory occupation!)
I have asked myself why?
In addition to the sexual exploitation you've already mentioned there are a number of other reasons why the post of governess was undesireable (thought not unsavory):
1. The governess was in an odd position in a household--above regular servants but below the family--she didn't really fit anywhere and in a less than pleasant situation it could be a very lonely life.
2. Each employer had their own rules as to how the governess should be treated and behave within the household. any slip-up, real or imagined, could lead not only to dismissal but the inability to find work again because the mistress of the house would tell all of her friends, who would tell all of their friends about whatever it was that got the governess fired. If the family were powerful enough, it would be very difficult to find work subsequently.
3. For a young woman born a gentleman's daughter, servitude in any form was a major step down. Jane Fairfax in Emma
was born into wealth, but the family lost their money and she was then orphaned into dependence upon female relatives who could not pursue any sort of action that would result in more income. She was kept in comfort as long as a wealthy friend needed a companion, but after that friend married Jane was sent back to her nearly penniless grandmother and aunt. Used to a life of privilege, she was faced with the possibility of having no choice but earn her living--unthinkable for a lady of her class.
In summary... The post of governess was respectable, but precarious. It left a lady heavily dependent on the goodwill of her employers. And it was a socially ambiguous position: a governess was a lady but also worked for pay--no other occupation of the time had such blurred lines of status.