Why high Main crank bolt torque

[raggen]

I am replacing the timing chain guides on my 2001 540. As most users, I had great difficulty getting the crankshaft bolt off, but got there in the end

Now I am considering why I have to replace the crankshaft bolt and why it is torqued so high.

I understand that if the bolt is torqued as per bmw spec it may stretch the bolt and weaken it.
Many posts say they have reused bolt, and i understand why as it is US$ 60 to buy in US and ship here to new Zealand

But why does the bolt need such a high torque? All it does is hold the harmonic balancer pully?

[CPHES]

To keep it from falling off at high rpm. Don’t fool with that. Look at the cost as an insurance policy. If it all comes apart on the road because you used a part that was not meant to be reused, the cost above is nothing. This is one of the reasonable costs of German engineering.

[jclausen]

Don't go cheap now, buy the bolt, its not for you to know the reason, just replace it.