Why do I need to install Realtek or Intel Graphics Driver software?

I just installed Windows 8.1 Professional on Acer Aspire 5738 from Dreamspark. I need to know whether there is any significant improvement in audio or graphics quality when I install Realtek audio driver (since obviously I can play songs without any issues) or Intel Graphics Driver for my laptop. Otherwise I could very well use the extra disk space to store my documents. What would I miss without them?

Thanks in advance.