Right, it's a different kind of mobility. It can be towed, but needs something to do the towing. The jeep based system probably can't shoot on the move either, so the difference is only slight. Being static isn't terribly bad considering how small it is (~how easy to hide), and being without a radar just makes it even more easy to keep hidden.
That configuration probably won't be defending field armies, but fixed assets as you suggested. The thing is, fixed assets are less likely to be under attack by low flying aircraft/helicopters these days, and I doubt this system would be effective against PGM.