Wrong.
Encryption is security through obscurity, just like MAC filtering.
No it's not. None of them have any obscuriy. Encryption can openly defined, it's just they keys/passphrases that are secret. Mac filtering has no obscurity at all.
One is far more difficult than the other, but they are more or less the same. The MAC is a 6 byte key that gets broadcast openly fairly often where as most people use far larger keys for encryption that aren't broadcast at all if possible, but in the end the principles are the same.
Please stop repeating things someone else said that you don't understand.
Security is built in layers, defense in depth. You use as many as you can/need. You ACCEPT that one or more of your security protocols CAN and WILL fail, but you design in the hope that enough of them will work to keep you safe.
Your argument is the height of ignorance. You're arguing that leaving your valuables out in the front yard near the street is just as secure as putting them in your home because you left the door unlocked, ignoring the fact that no one will see them inside the house so they won't know its there to steal. Sure, its easy to walk through then unlocked door, but thats already a step beyond what most people will do.
I'm not repeating something someone else said. Mac filtering is like having a doorman to whom you scream your name before getting into the building. Anyone in range can hear it, and pretend to be you by screaming your name.
Actual encryption is like having a key. Nobody can get in until you give them a copy of it (eg: tell them the password).