Price, availability and quality are the biggest reasons why Galils are not as popular as other rifles.
Price: Cheapest Galils I can think of start at or around $1600, you can pick up almost a dozen AKs. Seriously though, at $1,600 you can nab a Yugo SKS, a Bulgarian 5.45 and a Krinkov and have a wild good time.
Availability: Spare parts, magazines and just the rifles them selves are few and far between and all run at a premium prices. Parts kits are in the $500 IIRC, and Receivers are also in the $500.
Quality: While the ARM, ORF and IMA Galils are all top-notch awesome quality, companies like Hesse put out a horrid, low quality product, as are many of the off brand receivers and kits. One must be concerned about quality when shelling out 1200 for a Galil, because that is rather low.
Personally I think no one likes the Galil for the same reason no military uses them. They are not as cheap and common as an Ak and they don’t feature the excellent tactical add-ons and low recoil of an M-16. What you have a heavy rifle that fires .233 in an AK fashion, why not save $1200 and buy an AK-74 which will get you damn close to the same performance? And if you want .308, well FAL all the way.
My opinions,
Jack