They are on this budget. They hope to be on this budget, so they don't want to spend a lot. Plus that frees up resources for other things. Stocks or maybe something he can do through his 401k plan at work. In fact, that's what he should be doing because he's obviously got a long way to retirement.
Stocks are a long range investment.
This is where he can put his long range money. And the saving element is the short term. They need money. They want money to travel. They need money to fix up the house and for other emergency expenses.