While it is true one can go to a local bank and purchase rolls of half dollars (depending on availablity), many collectors have neither the time nor the patience for "treasure hunting" for better than 'hole-filler' grade Kennedys.  When starting out a collection, this may be the simplest route, but as time goes on, most wish to upgrade their collections, and it simply is not worth the hassle to sift through literally thousands of dollars worth of halves to do so.  The harder side of treasure hunting is finding the date/mint you want in a particular grade, and this is where buying coins on your wish list makes collecting much easier.  True, you may find some 40% silver, even maybe a '64 or Franklin, and yes, even a Walker.  However, by and large, putting together a roll of Brilliant Uncirculated or better Kennedy Halves is quite tedious, if not maddening at times!  And knowing HOW to grade is the key.  So, if you find yourself needing a particular roll of something there are two things you can do....knock  yourself out building it....or pay a visit to your friendly ebay listing!  Time is money...don't waste either!