I'm not sure that's true, but maybe your definition of "easily" is different than mine. Certainly that doesn't seem to be the case if you're working from salary alone.
Let's assume our developer enters the workforce at 24 and we're considering 38 to be "late 30s". Then she's worked 14 years, we'll assume at an average of $90K/yr, yielding 1.26 million in total income if you ignore interest, inflation, etc.
Various forms of tax will eat about 40% of that [1], so you're left with $756K out of the gate.
Suppose by shrewd living you're spending no more than 15% of your income on housing (which is half of the typical assumption), that's $189K over 14 years, leaving $567,000.
In 2005, the average cost of food at home for a family of 2 on a "moderate" plan was ~$475 (for a family of 4 that jumps to $675 to $810 depending upon the age of the children) [2]. Let's use $475 as an average. So that's another $79,000 for the 14 years (168 months), leaving you with $488,000 for a family of 2, or $453,600 for a family of 4.
So working from salary alone, you're under half a million just by taking into account quite frugal budgets for housing and food, and that's without accounting for costs of transportation, insurance, medical, entertainment, etc. let alone the costs of raising children.
I'm certain with the right decisions or investments it can be done, but I think if this were "easy" to do you'd see a lot more people with a lot more money in the bank.
[1] http://articles.moneycentral.msn.com/Taxes/Advice/YourRealTa... [2] http://www.cnpp.usda.gov/Publications/FoodPlans/2005/CostofF...