What makes you say that? How do you think militia worked?
It was a system based fundamentally on privately owned arms and ammunition; the point of the 2nd Amendment was to protect the militia by protecting the armed citizenry.
"...the right of the people to keep and bear arms..."
This is, pretty plainly, a right of people and not of governments, &c, &c. Some people say that, well, there is the militia clause, to try to support a reading where "the people" refers to their states or communities; but they rely on an incorrect understanding of the way militia worked to support that. Militia is not a synonym for army or gendarmerie.
There's still ambiguity there that doesn't specify private persons individually, because it appears to read as "the people" collectively as part of a regulated militia, not as private persons. The 2a wasn't written explicitly enough, but it's kind of moot at this point because the interpretation and convention equates to largely unhindered private ownership of all but automatic, compact, and/or explosive weapons of war that can also be privately-owned in some jurisdictions with additional costs and hurdles.
...because it appears to read as "the people" collectively as part of a regulated militia...
I'm not sure why anybody thinks a reading like that is plausible. I guess if you think of "militia" as a synonym for "army", it makes sense; but that's not how militia actually worked. If the 2nd Amendment had only been intended to protect a public or collective right to bear arms, it would have protected almost nothing and would not have prevented the militia from being disarmed.
There is a lot to say here but, in a nut shell, there was an obligation to be armed if one was in a militia, but there was no obligation to be in a militia if one was armed. There was no permit to purchase system or anything like that: the militia relied on ubiquitous availability of arms and ammunition in the private market. Although there were some town armories and magazines, this is not where the majority of service weapons were located -- the majority were in people's homes, as private property (property which they bought with their own money, retained when they aged out of service, and passed down in their estates).
This was a long standing institution in English society, having its roots in the 1181 Assize of Arms. I mean, it's not impossible that the founders were not thinking about this when they wrote the amendment; but it doesn't seem very plausible. If we consider how the militia actually worked, the militia aspect of the amendment and the private right aspect are aligned with each other.
