The OEM's customer is the carrier because the carrier determines whether or not the handset even appears for sale in the stores or on the website. For both the OEM and the carrier, updates are a pure cost center for which there is little-to-no benefit.
Google can't roll out updates on its own because the OEMs customize for their CPU, platform, baseband, etc. Google doesn't have the drivers, licenses, testing capacity, or configuration details to deal with the various bits of hardware.
Presumably Google could make regular updates a requirement for using Google services on Android. At that point we'd find out whether the tail wags the dog and I think Google might not like the answer; getting the data on Android users is quite valuable for building advertising profiles. I doubt a few Googlers desire to have timely updates would survive contact with the money-making ad side of the house but I could be wrong.
Plus it's in the OEMs interest to make the upgrade path involve purchasing a new handset.
If only. Actual low-ish spec phones can barely even lift the OS! By "do everything the OS demands" OEMs generally mean "sort of do it by hanging up in the process and requiring battery-removal powercycling". Source: spent three years using such a phone.
Only 1G of ram and 8G of storage, meaning only 3GB for apps, most of which are the stock Google ones, and 1G of ram means the thing crawls.
Moto is still releasing these anemic specs on the 3rd gen Moto G, only their "moto G turbo" will have respectable specs, and that's only in like Mexico or something.
And the company sells a phone lower than the G.
And this is a company that used to be owned by Google, and was branded as being a great stock android company during that phase.
I have a 1st gen Moto G. Bought it Dec 2013 and don't even care about having anything faster/bigger.
Indeed, the Moto E has been out for a little while and that phone is what I probably consider the bare minimum while still qualifying as a smart phone.
I'm just happy to have had device support for all these years so that I can run Android 5 natively and efficiently.
I assume you mean switching apps? Android doesn't have any paging support so if the app is in the foreground its entirely in memory.
Personally, I use Nexus devices... however, I still don't trust these devices enough for very sensitive stuff -- fixes for known escalation bugs can still take a while to get patched. :-/
Way too expensive in many countries, where pre-pay is the rule. No SD card nor replaceable batteries.
Regarding Nexus, I wouldn't trust Google since it screw owners with TI chipsets.
That's not a very good reason to not buy a Nexus phone, since every Nexus phone since the Nexus 4 has used a Qualcomm Snapdragon.
It doesn't mean that Qualcomm will stop producing Snapdragons.
But it also doesn't mean that some other reason, where Google also won't uphold its responsibilities to its clients won't happen.