Cost primarily.
Those units never go on sale. I waited until the 15% off site wide west marine sale they offer every Thanksgiving with free shipping. I'll have to admit that the install wasn't a lot of fun. I did the 4" sea scan 4 degree mount. I needed two extra hands and several more fingers to reach all of the bolts, washers, nuts etc. After several choice words and hands coated in 5200, it turned out great in the end.
It's a fun toy. I'm now considering adding an additional Lowrance chart plotter on the dash under my hds8 so I do not have to run split screen with radar/chart plotter.
Overtons has a great sale right now on the Lowrance hook chirp 7. Regular $600 on sale for $399.
Too many toys and too little time.
Good luck.
Cheers