Guid like this:
{"xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"}

that GUID is 32 digits long....
each 'digit' is a hex digit (0->9, A->E)
=> 2^4 values per digit, 32 digits
=> 2^(4*32) = 2^128 different GUIDs
(i.e. GUID is a 128-bit data structure)

Thats a number about 39 digits long!!!

Random integer (32-bit) = 2^32 different IDS
thats 10 digits, and now you have so many fewer options

Even with 64-bit integers, thats 2^64 different IDs, but u've still got 2^64 times fewer! which means only have a tiny percentage of what you can have with a GUID


however, if u used 4 random integers, or any struct/type with more than 128 bits, then this is just as good if not better. However, 128-bit was considered enough, and so to save space they just kept it at that.