While I generally agree with you (defense is more unpopular than the attack), there is one inherent difficulty even if there were enough players inclined to defend more: The time factor.
A smash'n'grab mission is easier to organize, because you can set a time in advance and wait until the necessary number of players finally has assembled on the launch base. The defenders have to react, and depending on the type of mission being inbound, the hardly have time to. Most players are in a sortie at the time the alert is triggered, and it takes a lot of time for them to finish their sortie and get to the base under attack.
Only very few players are probably willing to spend their time in the tower, watching the map for any incoming missions while everybody else is 'out there' and having fun.
Agreed on all counts, that's why I mentioned magic. I realize it's just unfortunately not practical in most cases.

The smash and grabs you just can't mount a reasonable defense against in time.
The thing that just makes me laugh and shake my head though is when you get a situation you can see developing for 2 or 3 sectors, that people call out 20-30 minutes before it gets there, and nobody ups to defend until there are 20 dots within a mile of the base and somebody calls 'Alert 103!!!' Sorry, I mean '*****************ALERT 103!!!!11!!!1!' on country and then gets irate when nobody beams in at altitude to defend.
I realize people are up to stuff a lot of the time, but with a situation like that you've got say, 10 minutes to get shot down/RTB, still gives you 10-20 minutes to get up to alt. If you're flying something that can climb that's plenty of time to get up for many of the attacks I see come in. Few people come in above 15k.
I quite often see these things develop, see someone call them out on country, and have time to get above all of them in a P-47D-11 before they get on dar. I say again, in a P-47D-11, usually without WEP!!!

If I can do it, anybody that likes flying Luftwaffe iron could be there in half the time.
But, it's not a popular mode of play. I've come to terms with that. I just wish it was sometimes. My favorite parts of the game are multi on multi engagements, and they just don't happen as often as I'd like.
Wiley.