POSIX prefers to codify existing behavior, and to only mandate new features or features that are not widely adopted when the existing behavior is unsatisfactory. Nowadays there isn't much call for presentation of data using unformatted text in fixed-width fonts, so column is unlikely to become mandatory. Unlike pr, it's from BSD, it isn't present System V and other historical unices, so it isn't grandfathered in.
Like any other text utility, you can express it in awk with a moderate amount of work. Here's a minimally tested implementation of column -t. Awk's -F option is similar to column's -s in simple cases (with a single character).
#!/usr/bin/env awk
{
if (max_column < NF) max_column = NF;
for (i = 1; i <= NF; i++) {
if (width[i] < length($i)) width[i] = length($i);
data[NR, i] = $i;
}
}
END {
for (i = 1; i < max_column; i++) format[i] = sprintf("%%-%ds ", width[i]);
format[max_column] = "%s\n";
for (k = 1; k <= NR; k++) {
for (i = 1; i <= max_column; i++) printf format[i], data[k, i];
}
}