Why should you build a mobile site or app instead of just resizing your desktop site for a smaller screen?
Desktop sites typically don’t load quickly on mobile devices.
Mobile users don’t need all the features a website can offer.
Mobile browsers aren’t powerful enough to load most desktop sites.
It’s a cheap way to provide a narrower set of options to mobile customers.
Does your site load quickly? Nearly half of all visitors will leave a mobile website if the pages don’t load within 3 seconds. Minimize loading time (the time it takes for a webpage to show up on your screen) so that visitors can quickly and easily navigate your website. Desktop sites typically don’t load quickly on mobile devices due to the design and size of elements.
Read more here: https://support.google.com/partners/answer/7323900