Indeed. Parsing files is a less robust way compared to calling some APIs or at least parsing some files with a schema (e.g. JSON or XML). For example, uptime(1) on Linux:
% strace uptime 2> /tmp/strace && grep proc /tmp/strace
17:35:24 up 3 days, 7:47, 1 user, load average: 2.29, 1.85, 1.56
openat(AT_FDCWD, "/usr/lib/libprocps.so.8", O_RDONLY|O_CLOEXEC) = 3
openat(AT_FDCWD, "/proc/self/auxv", O_RDONLY) = 3
openat(AT_FDCWD, "/proc/sys/kernel/osrelease", O_RDONLY) = 3
openat(AT_FDCWD, "/proc/self/auxv", O_RDONLY) = 3
openat(AT_FDCWD, "/proc/uptime", O_RDONLY) = 3
openat(AT_FDCWD, "/proc/loadavg", O_RDONLY) = 4
% strace uptime 2> /tmp/strace && grep proc /tmp/strace
17:35:24 up 3 days, 7:47, 1 user, load average: 2.29, 1.85, 1.56
openat(AT_FDCWD, "/usr/lib/libprocps.so.8", O_RDONLY|O_CLOEXEC) = 3
openat(AT_FDCWD, "/proc/self/auxv", O_RDONLY) = 3
openat(AT_FDCWD, "/proc/sys/kernel/osrelease", O_RDONLY) = 3
openat(AT_FDCWD, "/proc/self/auxv", O_RDONLY) = 3
openat(AT_FDCWD, "/proc/uptime", O_RDONLY) = 3
openat(AT_FDCWD, "/proc/loadavg", O_RDONLY) = 4