ipcalc - why it can't give correct network size by default

I found ipcalc didn't give correct network size when not specify the netmask,

In below result, it take the hosts count as 254, but not 2^24 -2,

eric@ePc:~$ ipcalc 101.12.12.12

Address:   101.12.12.12         01100101.00001100.00001100. 00001100
Netmask:   255.255.255.0 = 24   11111111.11111111.11111111. 00000000
Wildcard:  0.0.0.255            00000000.00000000.00000000. 11111111
=>
Network:   101.12.12.0/24       01100101.00001100.00001100. 00000000
HostMin:   101.12.12.1          01100101.00001100.00001100. 00000001
HostMax:   101.12.12.254        01100101.00001100.00001100. 11111110
Broadcast: 101.12.12.255        01100101.00001100.00001100. 11111111
Hosts/Net: 254                   Class A

But, if I give netmask by hand ipcalc 101.12.12.12/8, then it gives correct result.

I want to know: did ipcalc do this not properly? Or, ipv4 address are used in this way in real world?

Solution

classless inter domain routing was invented last century, since then it has not been practical to derive a netmask from a network address,

101.0.0.0 used to be a class A network, I don't know if it still is, neither does ipcalc.