IPv4 (which is based in binary but represented in base10 decimal) is running out of addresses. Back then people thought the number of addresses it had was so enormous that they would never run out so they gave out huge numbers of addresses to specific companies who use a tiny fraction of the actual addresses.

This problem has been made worse by cell phones which they didnt know at the time would be a computer in each persons pocket as well as internet of things devices.

So IPv6 (based in and represented in hexadecimal) has many many more addresses than IPv4.