The operating system has had this issue since the very beginning, and there is still no viable solution in sight. The main problem is that each company has to release their own updates for their Android devices, and in some cases this can take a lot of time if the manufacturer has to make special adjustments to improve the system for their specific product.
Samsung, for example, have been under some criticism in recent times for this aspect of their development. The company usually takes a while to prepare new versions of Android for their users, and they’ve become somewhat well-known for this fact as of recently.
According to experts, the delay in releasing a new Android version is usually tied to the complexity of the customizations introduced by the manufacturer – if a phone uses a version of Android closer to the core build, then it usually doesn’t take that long to bring out an update for it.
On the other hand, Motorola’s phones do usually come with various adjustments to the OS, including UI additions, so it’s sometimes surprising to see them working so fast and managing to deliver updates at their pace. Hopefully they are not going to decrease this trend in the future as it’s been earning them a lot of positive attention from their fans, and many people are currently happy with their Motorola devices.