This is a question that has confused me for a while. If a player fouls and pots the red when playing on a colour, their opponent gets 4 points, but they have taken a possible 8 points off of the table.
For example, if all of the colours are safe and a player is 32 points ahead having just potted the penultimate red, it could be worthwhile for them to pot the final red rather than play a safety shot. This would then put them 28 points ahead with just 27 points left on the table, compared with the alternative which would be 32 points ahead with 35 left on the table.
Of course, this example would be a deliberate foul and therefore could result in the frame being awarded to their opponent under Section 4.1 of the "OFFICIAL RULES OF THE GAMES OF SNOOKER AND ENGLISH BILLIARDS". However, it is still possible for an advantage to be gained where a player either pots a red accidentally or pots a red deliberately, but in such a way that it appears accidental.
I can't work out why the number of points for fouling a red isn't higher, or why a free ball isn't given to the opponent.