Some manufacturers limit rooting, promote their appstores, recomend to redownload a freshly installed app but now from them, have their 'antivirus' and 'cache' scanners, randomly unload background apps they think are less valuable from RAM and revoke their permissions while their own apps require additional permissions and accounts even though they just switch wallpapers or play videos. If we look at that, Google have much to implement and still have side-loading availiable, just very disencouraged.