That's a pretty wide ranging blanket statement. It shows a lack of knowledge, not an excess of it.

While MAC filtering does not do much to enhance security, it is useful for other things. For example, I use it in conjunction with "Static DHCP" so that when one of our laptops tries to connect wirelessly (using DHCP) my router recognizes it by it's MAC address and always assigns it the same IP address (keeping the same IP is not guarranteed with standard DHCP).

This is a convenience measure so that our laptops function as if they have static IP's when connected to my network, but still are using DHCP so that they can easily connect on other networks. It is not a security measure since MAC addresses can be spoofed. I use WPA for security. However, I only have the required amount of IP addresses in my DHCP pool and they obviously can't be assigned twice, so this MAC filtering does provide a (small) roadblock for inept hackers. But that is only a side effect, not my main reason for using MAC filtering.

Of course, if the OP had setup something like I'm doing, then he would know about it and could troubleshoot it if it were part of his problem. But a blanket statement saying "nobody uses MAC filtering" is just plain silly.