The problem is, they know you. Outsiders only see the book launches and signings, the thousands of books with the author's name blazoned across the covers, the requests for interviews, the opportunities to pontificate on blogs as if you knew what you were talking about but to your family you're anything but a writer. To my children I'm obviously only there to service their domestic requirements, to my siblings I'm the one without a proper job, to my mother I'm quite clearly as capable as the toddler I once was.
Respect at home is not part of the writer's life. After all, it's not a REAL job, is it? It doesn't require commuting or a briefcase or an office. You don't have to wear a suit or a tie or lace up shoes - if anything, your work wear is more likely to be a tracksuit and t shirt, or even pyjamas. If you're a mother, you may have been attracted to writing as a chance to combine parenting with work, but the end result is your little darlings will see your writing as something that can be fitted around all the other more important stuff, like running them into town because they missed the bus.
You're no use at helping with homework, obviously, because "they don't do it like that any more". And they don't - the worst mark my son got for English GCSE was on the only essay I helped him with. (Mind you, it would also have helped if either of us had ever read Julius Caesar.) Even if you get some kudos because someone's mother may have once read one of your books, it's tinged with amazement that anyone would do something so unlikely.
If you write commercial fiction your family may well sigh and suggest you might like to write something, well, sort of...better. By which, of course, they mean literary. (I suspect literary fiction writers are given helpful suggestions by their families to write something which, you know...pays the bills.)
No wonder writers like blogging and Twittering. For a few happy moments we can delude ourselves that someone, somewhere, takes us seriously. And I'd like to write a better punch line, but my daughter can't find her clean jeans anywhere and it's like, really important, and I've simply got to help her find them.
In case any one is interested, I'm running a class in Bath on Friday afternoons for 8 weeks over the summer, a mix of exercises and workshopping. Contact me for more details on email@example.com