The OnePlus 3 has 6GB of RAM, but people noticed that it doesn't keep as many apps in RAM as they expected. Carl Pei, co-founder of OnePlus, has addressed concerns about this on Twitter. .@LucaDuci we have a different strategy for RAM management that benefits battery. We think this is the best user experience. Carl Pei (@getpeid) June 17, 2016 First off, he says that limiting the number of background apps is to optimize battery life. Posters on XDA Developers have shown you can change build.prop to allow more background apps, but Pei points out there's more to RAM management than...
Source: http://www.gsmarena.com/carl_pei_addresses_oneplus_3s_ram_management_its_about_the_battery-news-18924.php