The earliest censuses of population Web use in the mid 90s had triple-digit numbers for those of us under the age of 10. We're looking at kids under the age of 10 (or more realistically I would say 7-8) because that's early enough for people's worldviews to be influenced by the availability of a tool. A child who doesn't see or ride in a car until they're 12 is still going to remember horses as default, remember thinking like a person did before cars, etc. A child who rides in a car at 3? Lived in a world that always had cars, which is going to impact how they view distance, travel, etc. Language learning is another example: Learning another tongue at 12 means you're not a native speaker. A 2-3 year old is. Internet use is similar.

Some things to consider are:

- The age matters. As late as 2000 (so kids born in 1995 who still aren't 30), 25% of 5 year olds used the Internet. At all. And an 'internet user' was usually defined with a minimum of once a week (or even rarer) usage. Not enough to really shape your worldview or how you approach problems.

- Most young (early elementary or younger) kids with internet access pre 1997 would only have it at school. These conditions meant most of the children in this age group would have had very close, direct adult supervision the entire time, which prevents it from being a part of a digital childhood since a digital childhood requires making decisions and acting online.

- To be an early adopter of the Internet at the time as a young child required literacy skills years ahead of your peers. In addition, you needed home computer access and the ability/permission to use it independently. To be so into it that you did enough of your socializing online to assimilate this new method of communicating into your core social programming also meant you needed to possess one of the few interests that the Web at the time was useful for. (I really liked anime, astronomy, video games, and programming so I spent a lot of time online).

Basically a lot of people in their 30s used the Internet before the age of 18, but not often enough at a young enough age for it to have really embedded it as fundamental in the same way. For that I think there's a critical period/age limit of about 7. To use the web between 93 (first home access) and 97 that young required skills/intelligence (literacy being the big one, but also simple things like 'hand eye coordination to deal with old mice' and 'knowledge of how to use a browser' that seem second nature now but when you're 6 with zero experience can be substantial), parents with the wealth and interest to have a home computer, and parents that would let you use said home computer for your own purposes/independently. (As opposed to now where everybody hands their kid a phone). The combination of ability, access, and freedom was rare.

I think a lot of people in their 30s and 40s are sort of in between: They're proficient but it's still learned, not hard wired/unconscious the way it is for those of us who were exposed very young. It's the difference between a habit and an ingrained physical task like walking.

In terms of why it matters, some examples of differences I'd consider are:

* Internalizing that independent authorities exist that you can contact that are outside of your adults' sphere of influence. Or read, or watch, etc.

* Internalizing that information is/should be available in your home/private spaces instead of it being something you had to physically seek out.

* Conceiving of ignorance as rude/willful by default instead of innocuous.

tl;dr: Lots of 80s and 90s kids online once in a while and at older ages, very few truly embedded in it the way kids are now due to resource and skill gates that have since been removed (you can use an iPhone without knowing how to read and there's a lot of multimedia online now + most kids can get their hands on a phone).