The default handler for SIGINFO is a non-fatal process summary, like this (from FreeBSD):

    load: 0.15  cmd: sleep 52109 [nanslp] 0.27r 0.00u 0.00s 0% 2132k
    mi_switch+0xc2 sleepq_catch_signals+0x2e6 sleepq_timedwait_sig+0x12 _sleep+0x1d1 kern_clock_nanosleep+0x1c1 sys_nanosleep+0x3b amd64_syscall+0x10c fast_syscall_common+0xf8

SIGUSR1's default is to terminate the process, which makes it awkward to use as a SIGINFO alternative on platforms without it.