Why can only root can mount cifs

On ubuntu or kubuntu I install cifs-utils, then mkdir and added a folder to /media, then added some lines (as I normally do with a new ubuntu install) to /etc/fstab so that on boot it mounts a samba from the basement to /media and I can use it like an external hard drive. I prefer this option so that it doesn’t feel like I’m using a remote hard drive, but a local external drive.
The problem is this when selecting that folder: Mount only root can mount //192.168.0.20/mainshare on /media/mainshare

The same credentials in /etc/fstab are used for every other ubuntu install on the network
//192.168.0.20/mainshare /media/mainshare guest,uid=1000 0 0

Workaround is: upon login open a terminal and type: sudo mount -a
Not a long term fix.
Why can only root do this in MATE 1604

Turns out you have to add “user” to the options and it will mount properly.