Punctuality records in the UK are based on up to 15 minutes off stand.
However depending on a length of flight it can depend on how much time a flight can make up. It's also much harder if it's a low cost carrier where all the times are kept to the minimum to start with. This can cause a knock on effect for the rest of the days flights.
Some airlines that operate shuttle services into a hub for onward connections. It is not just the passengers you need to think of but the crew may not all be operating the same flight for the onward connection.
So not only do you have to worry about the passengers on your flight that may miss connections. But if all crew are operating on seperate flights and different aircraft then in theory you may in total cause delays to 4 or 5 other flights depending on number of crew operating.