you don't see why? it's like this: take her monthly ss checks & invest them to continue to grow our nest egg. i am 67% of the way to my goals & every dollar invested brings me closer to reaching my goal.
Greg's point is a good one it isn't the nest egg it is the retirement income.
This might help to put some real numbers. Let's say your desired retirement is 80K, this would require saving of $2 million using the 4% SWR rule of thumb.
If she collection $718/month= $8616/year in income, meaning you only need 2,000,000 - ($8,616*25) = $1,784,600 to get 80K in retirement.
If she wait until 66. You'll need $2,000,000 - ($952/month*12 *25)= 1,714,400. The $70K difference in the size of the nest egg is important.
Of course if she starts collecting at 62 she collect $8616/year for four years, which you can use toward increasing your nest egg. However obviously there is no way that saving $8616 for 4 years is going to let you accumulate an extra $70K without some amazing luck in investing. So strictly from a longevity risk you are better off waiting.
Of course there is a chance that your wife may died at age 70 or even earlier so you would be better taking the money earlier, SS payments are designed to be actuarially even so on average you'll collect the same amount of money no matter when you first starting taking them. This is assuming all things are even.
However, all things aren't even. Right now with 200K+ income it looks like you are in the 33% marginal tax bracket or near the top of the 28% bracket. Add say 7% for state income and your near 40% marginal rate. After you retire the numbers will drop to probably 25% and couple of points less for state income. So roughly speaking you'll pay 10% less tax on her larger check if you wait to collect them when you are retired. You should run the number on your own, but I suspect you'll be better off waiting if you want to maximize your retirement income.