I'm not sure that I know the answer. The cabin size could have something to so with it, but it's not really that big of an issue for most people. After all, how often do your really load one up to the gills with 7 to 9 people and blast off on a 2800 nm leg? Most of the airplanes have all of the expected passenger comfort stuff - full size flushing lav, hot water in the sink, galley and microwave, entertainment center, etc. On the typical trip the room is more than adequate and it's actually a pretty pleasant place to spend a few hours.
Personally, I think that there is some prejudice with it being an Israeli built airplane. If you want to get technical about it, it's probably best described as being built in the U.S. and assembled in Israel - engines, avionics, brakes, tires, and most of the airframe components are built in the U.S. Someone once told me that the only components built in Israel were the landing gear struts. Whether or not that's true, I couldn't say.
In the past there were product support issues, but Gulfstream has allayed any of those fears. There were also issues in the past concerning the reliability of the slat/flap system, but those issues have been resolved. (It's amazing what happens when the things are maintained properly.)
There are a lot of pilots out there that scoff at the idea of pneumatic boots on a modern bizjet. Say what you want, but when it comes to climb performance in icing conditions, I'll put my SPX against your Lear or Falcon any day. Boots are essentially a non-issue and in my opinion they have more pluses than minuses.
When it comes to airplanes (especially jet airplanes), everything is a compromise of one sort or another. The only way I know to figure out which one best fits a specific set of mission and budget constraints is to do it the old fashioned way - be honest with your requirements then list each of the candidates with their respective pluses and minuses. Crude, but effective. Like any other light to mid-size jet out there, the Astra has it's fair share of compromises, that being said, it's still is the most bang for the buck out there.
I've seen operator after operator fly them for a few years then, when the time comes, sell them for more than they paid in the first place.
'Sled