That's just because there are fewer steps for finding a simple derivative.

If you evaluate 12326 in your head, most people probably end up thinking through something like this

    123 * 20 + 123 * 6

    123 * 20 
    123 * 10 * 2
    1230 * 2
    2460 Now remember this part

    123 * 6

    100*6 + 20*6 + 3*6
    100*6 = 600
    20*6 = 120
    3*6 = 18
    600+120+18
    738

    2460 + 738 = 3198

Now compare that to taking a simple derivative.

Although I could ask you to take the derivative of 123x^26.