This is a bit different than the way Android updates are handled. After Google releases a new Android build, the carriers test it and then send it out themselves. With this method, Android users have to wait for each carrier to be satisfied before the update is disseminated. Since some carriers take longer to test updates than others, the result is an unbalanced process. Different owners of the same phone could have their handsets running on different builds of the same OS at the same time, depending on which carrier they subscribe to. It is this uneven experience that Microsoft is looking to avoid.
Microsoft’s updating process still includes the carriers, unlike Apple. The latter has complete control when sending out iOS updates, leaving it to the company’s discretion when the next iOS build is sent out.
Microsoft did say that it plans on keeping Windows 10 Mobile fresh by sending out updates at regular intervals.
source: WMPoweruser