Page speed can really change the users' experience on your website. People get even more impatient when looking at websites from their mobiles. Nobody wants to wait for too long when the page is loading, especially when experiencing a mediocre connection while sitting on the bus or a train. If your page speed is really slow it can lead to the users leaving your website faster and even avoiding it in the future.
Now along these extremely important for your business reasons, Google just added a new, SEO-related one - your mobile page will rank lower in the mobile searches if it's too slow.
Most websites will not be affected by the change, as it "will only affect pages that deliver the slowest experience to users" , however Google recommends you to check their guidelines on performance and user experience metrics to make sure your website provides the best it can to the user.
Google has already been using page speed as a factor for the desktop searches ranks for years, but with this announcement it will finally make our mobile search experience better.
The update will come into effect in July 2018, so make sure to have a look at your mobile page speed before then!