[CentOS] firewalld services

I am familiar with using commands like:

firewall-cmd --permanent --add-service=http

To enable firewalld services.  I am also aware that this is through xml 
'scripts' in:

/usr/lib/firewalld/services/

But what I find interesting is what services are there and which are 
not.  I went a'lookin with:

grep "port=" /usr/lib/firewalld/services/*|more

And found some like:

http, https, imaps, smtp, and pop3s

What I do not find are others that I would think are 'standard' like:

pop3 (110) and imap (143)

I can understand 587 not being included, but imap?

I can always just add them with:

firewall-cmd --permanent --add-port=587/tcp

But I want to use the standard files.  Perhaps because they are there.  
Have I missed how some are handled?

thanks