Benefits of setting PHP memory_limit to lower value for specific PHP script?

Benefits of setting PHP memory_limit to lower value for specific PHP script?

I need to execute just few lines of PHP code on every single page of my
website. This PHP code does not require more than 4MB memory. That is why
i want to allocate just 4MB memory to all pages by using following code :
ini_set('memory_limit','4M');
Does it give any benfits in any of the following areas :
1. Website speed
2. Bandwidth optimization
3. Optimizing server memory usage