Iterators std::multimap and std::deque

Please tell me why std::deque - you can add a "step" to the iterator, but it doesn't work for std::multimap ?

#include <iostream>
#include <deque>
#include <map>

int main()
{    
    std::deque<int>my_deq;
    std::deque<int>::iterator iterator_deq;
    iterator_deq = my_deq.begin() + 1;    

    std::multimap<std::string, int>my_multimap;
    std::multimap<std::string, int>::iterator iterator;
    iterator = my_multimap.begin() + 1;       //This is not possible, VS2019 gives an error.    
}