Apple’s products are used by a large number of people around the globe and Google pays a lot of money to make sure that its search engine is the default among iOS devices.
It is unknown the exact amount that Google pays Apple to be its default search engine since there hasn’t been an official number since 2014. Back in 2014, there was a court document that revealed Google was paying Apple $1 billion, but it is now estimated that this number has gone way up and is getting higher each year. Goldman Sachs analyst Rod Hall believes that Google is now paying Apple $9 billion and he expects this number to rise to $12 billion in 2019. It is unknown how accurate these figures are since Apple and Google have not released anything on the matter since 2014.
It is possible to change the default search engine in Safari, but most people just end up sticking with Google. Back in 2013, Apple also decided to change Siri so that when it does a search, it does not use Google but instead uses Bing. This usually causes Siri to get mixed results from many users when doing searches.
This may seem like a large amount of money to pay but Goldman Sachs believes that this is just a fraction of the profit that Google is making since so many households own Apple devices that use Safari.