Well, actually it did.

Some of the reasons are:

1) Most applications use very reliable databases as a store. Back in the day, programmers used to write their own one-off BTREE libraries, which stopped with msql/mysql, jet, dbm and sqlite.

(A holdover from that era is when interviewers asked you to roll your own sort algorithm, which you should almost never do for production apps.)

2) Some software is fuzzed.

3) Some software has managed memory.

4) Some software has tests.