Why is it necessary to fix social security and medicare?

Medicare is expected to run through its trust in about 10 years or so, maybe less, and so the complaint seems to be at that point we would be spending more than it makes. Same with Social Security which might last 15 or 20 years if best case. Of course right around the time the trusts dry up we should see a constant high death rate amongst beneficiaries, so in theory I suspect it would turn into a positive income within a few years but I have never seen any data on that from either side. My point is that the if you remove medicare and social security taxes and expensed, we still have a huge defecit issue and so why are we concerned with programs that pay for themselves when we can't pay for any other program in the US budget. I mean we don't cut social security, not one time even though it's been making a positive budget balance until just a year or two ago. So why do we only talk about cutting taxes that are illegal which affect the rich but not cutting these illegal social security or medicare tax. Hey i'm with republicans, taxes slow growth, so why not cut hohse taxes as we cut those benefits?