Because the fields are there for humans, in the packet itself it’s a 32bit integer, and you can’t just arbitrarily make the src/dest fields in the packet bigger— it stops being IPv4 then.
It's a fact of life that working with networking that we'll have to work with IP addresses at some level. It's easy to tell someone, "hey try typing in 'ping 8.8.8.8' and tell me what you get".
The readability of IPv6 is, in my opinion, worse with repeated symbols and more characters to remember. The symbols that were chosen were also poorly thought out. Colons are used in networking a lot of times when you want to connect to a service on a particular port, so if you want to visit 2001:4860:4860::8888 in your browser, you have to enclose the address in square brackets.
The wackiest example I've seen of this is the `ipv6-literal.net` notation for Windows UNC paths: https://devblogs.microsoft.com/oldnewthing/20100915-00/?p=12...