Take your pick (probably a combination of the below):
1) it is more popular then what they are using, developing or have skills for
1a) they use language x which does something different that they feel PHP sucks because the lack of it.
2) they got stuck using it and prefer language y instead.
3) They really aren’t all that good programmers and rely on pre-implemented security features to save their butts, and PHP doesn’t meet their dependencies
4) they are invested-in or represent language/platform x and PHP is a compelling contender.
5) they prefer to argue instead of fostering as accessible/usable alternatives for for one reason or another
Just as COBOL, FORTRAN, Visual BASIC, Perl, etc. are reviled by some, they still get jobs done. In some respects it may suck, others it's just fine partly based on intended application and/or coding skill.
If PHP was so bad in all the respects argued, there would be a much more compelling alternative, but it isn't all that bad, and actually quite useful... and popular.
1) it is more popular then what they are using, developing or have skills for
1a) they use language x which does something different that they feel PHP sucks because the lack of it.
2) they got stuck using it and prefer language y instead.
3) They really aren’t all that good programmers and rely on pre-implemented security features to save their butts, and PHP doesn’t meet their dependencies
4) they are invested-in or represent language/platform x and PHP is a compelling contender.
5) they prefer to argue instead of fostering as accessible/usable alternatives for for one reason or another
Just as COBOL, FORTRAN, Visual BASIC, Perl, etc. are reviled by some, they still get jobs done. In some respects it may suck, others it's just fine partly based on intended application and/or coding skill.
If PHP was so bad in all the respects argued, there would be a much more compelling alternative, but it isn't all that bad, and actually quite useful... and popular.