Upload speed is used for establish a data verification connection between your modem and ISP Server. A small token has been sent from here to ISP for checking proper connection and no error.So its need very low speed for sending token for establishing connection and downloading that's reason usually uploading speed becomes as much slow user can work easily.
A typical web browsing session might involve several small requests sent from your computer to remote sites requesting pages (anything sent from your computer to the internet is an "upload", including requests to fetch pages), but the size of the pages and what they contain typically dwarfs the size of the original request by factors of 100 or even 1000 or more at times. A tiny 200 byte request for a YouTube video being uploaded could result in a download of many millions of bytes.
It won't matter to you that the upload of that tiny request is somewhat slower as long as that huge download is as fast as it can possibly be.
The designers of the various technologies that we use to connect to the internet have realized this, and use it to "shift the balance" in your connection. Whereas in the past you might have seen 50/50 allocation in your bandwidth - half for uploading and half for downloading - the technologies being implemented in many cases effectively take away some of the uploading capacity in order to make the downloading speeds faster. Perhaps an 80/20 allocation of the available capacity instead: downloads are faster because you do them more, uploads are slower but you're likely not to notice or care."