pg_atoi()

Is there a reason why pg_atoi() was programmed to fail if the entire
input string is not valid?
i.e. "109" yields 109, but "109 apples" yields an error.

Snippet from pg_atoi() in src/backend/utils/adt/numutils.c:

l = strtol(s, &badp, 10);

if (errno) /* strtol must set ERANGE */
elog(ERROR, "pg_atoi: error reading \"%s\": %m", s);
if (badp && *badp && (*badp != c))
elog(ERROR, "pg_atoi: error in \"%s\": can\'t parse
\"%s\"", s, badp);

Thanks,

R.