Actually, they do... and why would you want to catch that in the first place? It's a coding error which you catch while testing your code.

well, assume you change the name of an methode. in a big project, it takes hours / days to make sure, all affected places have been adjusted. to find the missing ones you have either to get the "white page" (error page) yourself, a customer has to provide the info or you would have to look for "fatal error..." in the error logs of php. having this catchable, i could make php send me a nice email with backtrace when such an error occurs... :)

also when dealing with higly dynamic objects it could be very usefull to find logic/programming errors, which only occur in a special context. without a backtrace (with the internal php fatal error unluckily does not output), it's very hard to debug such errors.