Yes, you can work out the cost of deferral yourself, and Grannygrumps1 (love the name!) that may apply to you, but not to everyone. So many factors - the age at which you can claim, the amount you can claim etc.
For some years, interest rates were very low. So, if you claimed but didn't need it, and put it straight into savings, you wouldn't get so much interest. Now interest rates are going up - probably not enough to be significant, but it is another factor.
Also, obviously, is the age at which you expect to die! I did a rough calculation based on average life expectancy in my area, adjusted for family factors.
I quite like doing all the calculations, but I do see that some wouldn't!