speaking from my own experience as a youngster on the internet when it was literally first born (I dialed into it via a 9600 baud modem to my local library and used Lynx on a VAX system... I never even knew the internet had fckn colors until dial-up arrived a few years later and could use Netscape LOL.... Back then, I was never out to cause anything malicious, I just enjoyed learning ways to do stuff that were "different" and back then, things were much more simpler as well, but it was also like the wild west of computing, similar to 2013-2014 for BTC lol...
That said, I think a lot of people are just out for a challenge , or just to learn. Sometimes it may cause damage, ofc, but personally I never broke anything that I'm aware of. I just tried to learn as much as I could about TCP/IP and networking etc... Nowadays, there are so many attack vectors that it's much easier than back then to exploit for gain - In my days, all there was was literally Yahoo search, and a fuckin bunch of UNI servers hosting Unix software lol... I remember telnet was very fun back then too...
Anyhow, I think many people just do it to learn, but nowadays, it's very easy for a very smart (and scammy)! person to find exploits... The more code that exists, the more exploits to be found and so on ... 🤷♂️