18 months does not seem extreme for people paid as well as software developers, although "easily accessible" might be better than sitting in a savings account.
That's true. The general rule I go by is carry between 3-5 months worth of expenses (debt service + living expenses) in cash and the rest goes into various investments to make more money. The cash is my emergency fund and the investments are my savings.
If you leave 18 months worth of cash in a savings account, you're losing value to inflation.
Under normal circumstances I would agree with you. Locally, if it takes a software developer 3 months to find a job it means that they took a 2 to 2 and a half month vacation. On the other hand, almost all the software jobs locally are defense related and with all the pending budget uncertainty(combined with volatility in stock and bond markets) I am currently carrying in excess of 1 year expenses, for my definition of expenses.
It's simple: Savings are the money you have left over after your expenses. It's easier to save money when you're making enough to live comfortably and then some. (And I know people will talk about how you can live below your means with any level of pay, and that's mostly true, but the "Rice and beans again tonight" simplicity you need to save money on a shoestring budget is way harder for most people than the "Resist the urge to buy a yacht" simplicity you need to save money when you're making six figures.)
Because after a certain point it's your own fault for not saving a bit. People who make less money have fewer options because you can only cut back so much on food and rent.
A person making $20k a year doesn't have much flexibility. They'll have problems just getting by, much less saving 18 months of expenses.
On the other hand, a person making $100k a year can always pretend they only make the $20k and save the rest. Or they can live more comfortably and still save some money. Or they can spend with reckless abandon and save nothing.
