SSDI or not??

I am disabled from a progressive neuromuscular disease;  I worked until I could not work any longer.  I have not applied for SSDI and don’t intend to.  Why not?  I suppose that I could spend the money but in all honesty, I don’t really need it.  I know people whose disability has caused them real hardship and they flat need the money but I don’t.  I do plan to draw my Social Security when I turn 66 because by then DH will be retired (maybe) and we will be drawing down our retirement savings.  My sister-in-law thinks I’m dumb not to take the SSDI and maybe I am…but then maybe I’m happy with enough.