Teams normally “enforce” the follow-on in cricket to increase their chances of bowling out the other team twice and winning. A team will most commonly choose not to enforce the follow on based on the physical condition of both players and the pitch.
The follow-on is an option available to the team that batted first if they have a lead of at least a certain figure after each team has batted once. Often this is 200 in a test match and 150 in other first class matches. Enforcing the follow-on means the other team must bat again, overriding the usual rule that teams take turns to bat.
It’s possible the team that followed-on is still behind after their second innings, meaning they suffer an “innings defeat.” Even if the other team gets ahead after two innings, their lead will often be low enough to easily overtake quickly. The big advantage of the follow-on is that it reduces the chance of the game ending in a draw before the opponents have been bowled out twice. It can also demoralise the other team, being forced to bat again immediately, highlighting their deficit.
While enforcing the follow-on might seem like a no-brainer given this advantage, teams don’t always do it. One reason is that this would require the entire team to return to bowling and fielding without a break, increasing mental and physical strain. This can be a more important factor if key players are already carrying injuries or if important games are coming up soon afterwards.
Another reason not to enforce the follow-on is if the pitch is deteriorating consistently. Waiting longer before the other team bats could make it easier to bowl them out, particularly with spin bowling.
A rare possible scenario for not enforcing the follow-on is if the team is more concerned about avoiding defeat at any cost than pushing for a victory. This could happen if a draw would be enough to win a series or to achieve a particular league position. Even if enforcing the follow-on was the best option to increase the chances of winning, it might also increase the risk (however small) of losing. Not enforcing the follow-on inherently increases the chances of a draw.
As always with first class matches, the decision whether to enforce the follow-on will depend on the weather forecast. If rain is likely and play could be lost, enforcing the follow-on may seem a safer option than if the game was expected to play out in full.