Why can't butt implants be saline?

 Good question but I can tell you the reasons you would not want sailine buttock implants. Firstly, the buttock sustains much more daily activity and trama by going about your day, climbing stairs, sitting for long periods of times, lying down for hours, and not infrequently falling onto your butt therefore creating a much higher risk for rupture of the implant. Secondly, a saline implant would be difficult to create that will hold it’s 3-dimensional shape as well as a semi-solid silicone rubber implant. And finally, believe you’re not, a saline implant  would probably feel the most unnatural of all. Hope this helps. 

   I think that there is certainly a desire to create a softer implant that will not rupture, but the rupture issue is the primary concern.