Dinesh Kartik - Party Pooper?

In the 2 one-days that Kartik played against Sri Lanka when Dhoni was banned here is a text of the commentary (taken from cricinfo):

 

1)       24^th Dec 2009, India vs. Sri Lanka at Eden Gardens

This match made history of sorts as no tickets were sold!!! Yes, you can have empty stadiums in India for a cricket match.

 

Anyway, back to the topic, so far Kartik has been playing run a ball while Gambhir has been doing the entire run making to get India close to victory. Kartik hits his first four when not only is India in a comfortable position to win (7 runs in 14 balls, 7 wickets in hand) but more importantly Gambhir is 4 short of a milestone – 150. Why does Kartik have to go for a boundary when he can let Gambhir take the strike and get his 150 rather comfortably and perhaps go beyond 150 to get his highest score in ODI’s?

 

Luckily for Gambhir he did hit a 4 as India’s winning runs and also his 150 although he could not score more than his highest ODI score (of 150).

 

Just three to win it. A four will also get Gambhit to 150.
End of over 48 (9 runs) India 313/3 (3 runs required from 12 balls, RR: 6.52, RRR: 1.50) KD Karthik    19* (22b 1x4)      RAS Lakmal    10-0-55-2 G Gambhir    146* (136b 13x4)      SL Malinga    9-0-71-0
47.6	Lakmal to Karthik, no run, another bouncer down the stumps, getting him to crouch low
47.5	Lakmal to Karthik, FOUR, on the full, driven on the rise to extra cover where Malinga tries to stop the ball with his feet but makes a total mess of it
47.4	Lakmal to Gambhir, 1 run, another short ball, to which Gambhir arches his back and uppercuts it down on the bounce to third man
47.3	Lakmal to Karthik, 1 run, straighter ball on middle and off, punched down to mid-on
47.2	Lakmal to Karthik, no run, another slow bouncer down the stumps and he ducks under it
47.1	Lakmal to Gambhir, 3 runs, pokes at one on a length outside off and gets an inside edge past leg stump

 

2)       21^st December, 2009, India vs. Sri Lanka, 3^rd ODI at Cuttack.

 

In this situation again the man is scoring about a run a ball and Tendulkar on the other end is doing the entire run making. Again, India is in a very comfortable situation and victory is guaranteed. Kartik hits a six when Tendulkar was on 91 and India needed 13 runs to win with 7 wickets in hand and 8 overs remaining. In fact in the previous over he had hit a 4. With the six India needed only 7 to win which meant Tendulkar would most likely miss an ODI century.

 

41.5	Randiv to Karthik, SIX, maximum! Dances out, collects on the full, and dumps it over long-on
41.6	Randiv to Karthik, no run, pitches outside leg and he turns it to midwicket
End of over 42 (7 runs) India 233/3 (7 runs required from 48 balls, RR: 5.54, RRR: 0.87) KD Karthik    32* (30b 4x4 1x6)      S Randiv    8-1-33-1 SR Tendulkar    91* (102b 12x4)      SL Malinga    9-1-46-0
Seven to win. Two fours for Tendulkar?

 

What is the point of hitting a six when your batting has been lacklustre throughout and the person on the other end is closing on a milestone?

 

Why would someone do that?