The whole point of hiring a lawyer is to get customized legal advice or documents that pertain to your situation. If you're happy with using general advice/documents that may not actually fit your needs, you're free not to hire a lawyer.
It's basically the same as the choice between using stock Wordpress or hiring a developer to customize it for you (or to make you a custom CMS), except that the consequences are usually more dire.
Also, some of your examples are a bit odd. I don't know anyone who's hired a lawyer to buy a house or hire a housekeeper/nanny/gardener--is that some sort of weird Silicon Valley practice?
Disclaimer: I am not a lawyer, this is not legal advice, ask a lawyer acquaintance of yours instead of trusting me if this is any more than idle curiosity.
A lawyer's job when buying a house is mostly dealing with the mortgage. They can explain the mortgage paperwork to you, and find traps like balloon payments or weird escrow structures that a layman might miss. If you pay out of pocket, there's generally a lot less for a lawyer to do.
There are of course exceptions where a lawyer is very important, like reviewing the bylaws of a condominium or homeowners' association, or explaining unusual clauses in the sale contract. Unfortunately it's hard to tell when you've run into one of these without having past experience or hiring a lawyer.
It's basically the same as the choice between using stock Wordpress or hiring a developer to customize it for you (or to make you a custom CMS), except that the consequences are usually more dire.
Also, some of your examples are a bit odd. I don't know anyone who's hired a lawyer to buy a house or hire a housekeeper/nanny/gardener--is that some sort of weird Silicon Valley practice?