Most players these days SV at 40-0 5-3 or something. Very rarely someone like Tsonga will do it on a 2nd serve breakpoint down
Pete just got more aggressive as time went on. He probably thought as he got older that SV-ing on nearly everything could win him 7 wimbledons it would be effective elsewhere. Plus it saved him from getting too knackered as he got older. To compare 2 marathons look at sampras v correja 1996 and sampras rusedski 2002 and see how much more aggressive he is (although 1996 levels is still way higher than most today)