Those are reason why you wouldn't use groff, it still doesn't explain why – if you're taking the effort – you're not building a proper roff replacement, but some subset bastard program. And then hack stuff like tbl into the main executable. (Never mind that there's Plan 9 roff or the heirloom version)

I get it, nobody really seems to use non-man roff anymore. Still, subsetting and reinventing the wheel (partially) seems a odd solution for this.