Question: Difficulties to compute a definite integral.

Does anyone have any idea why Maple can obtain a closed form of 

Int(f, t=1..3);

but doesn't for 

Int(g, t=1..3);


The Int forms are quite close and I don't understand what makes Maple's task that difficult in the second case (the issue seems to come from the conditions in the piecewise function).
Can we force Maple to perform the second integration ?




`Standard Worksheet Interface, Maple 2015.2, Mac OS X, December 21 2015 Build ID 1097895`


f := piecewise(z/t < 0, 0, z/t < 1, 630*z^8/t^8-2520*z^7/t^7+3780*z^6/t^6-2520*z^5/t^5+630*z^4/t^4, 0)/t:

Int(f, t=1..3);

value(%);  # returns a closed form of the integral

g := piecewise(z/t < 1, 0, z/t < 2, 10080-60480*z/t+156240*z^2/t^2-226800*z^3/t^3+202230*z^4/t^4-113400*z^5/t^5+39060*z^6/t^6-7560*z^7/t^7+630*z^8/t^8, 0)/t:

Int(g, t=1..3);

value(%): # unable to return a closed form of the integral


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