Why do we use dynamic memory allocation in general and why did we use it in this particular example? [closed]

Question

Dynamic Programming C/C++ implementation of LIS(Longest Increasing Subsequence) problem

/* lis() returns the length of the longest increasing
subsequence in arr[] of size n */

int lis( int arr[], int n )
{
int *lis, i, j, max = 0;
lis = (int*) malloc ( sizeof( int ) * n );

/* Initialize LIS values for all indexes */
for (i = 0; i < n; i++ )
    lis[i] = 1;

/* Compute optimized LIS values in bottom up manner */
for (i = 1; i < n; i++ )
    for (j = 0; j < i; j++ ) 
        if ( arr[i] > arr[j] && lis[i] < lis[j] + 1)
            lis[i] = lis[j] + 1;

/* Pick maximum of all LIS values */
for (i = 0; i < n; i++ )
    if (max < lis[i])
        max = lis[i];

/* Free memory to avoid memory leak */
free(lis);
return max;
}

It is a code from www.geeksforgeeks.org . I have seen explanations that memory is allocated(when done dynamically) on heap, which is a free store of (very large) memory, so it makes sense to only use dynamic allocation when memory required exceeds memory of stack used for storing variables and data locally allocated in functions.

Would it make a difference if I declared array as int arr[n] (as n is given by user in input) and then in main function use lis(arr, n) ? If so, why? If not, what else does dynamic allocation benefit from in this case and in general?