Personally.. I think "because we can" is probably the answer. Who knows what kind of info they are scoping up.
There's definitely an issue on on the collection of data, and i think the majority of the issue is either because the companies cant be trusted to keep it safe, or the governments are completely incompetent to be trusted with it.
The fact is although ways of gathering data have increased, so have ways of keeping it private, which is a good thing. The ability was always there, the internet was never private.
I've no idea where some of these decisions come from, I imagine plenty from from well meaning thoughts, but implementations have far reaching consequences and terrible side effects.
On the other hand at the current state of things, analysing your writing style probably isn't on anyone's agenda but googles so they can give you more services and keep you on their platform. Unless your specifically a target of course.
You bring up a point about not meaning your a criminal which is a good point. All this data collection may have no consequence now, the government might hover up a bunch and not care, there only looking for specific things. But what about future governments?
One thing they all seem to disregard is how the data will be used in the future, you cannot guarantee it wont be misused. With google you at least have an option to delete data, decide whats public and private, with government you don't even know what they have.
An issue as well even if you decided to open up information about you, you put yourself at risk in other countries, since even though where in this weird data collecting spying prying "think of the childeren" age, many countries are in the data gathering spying prying "oh look you dont like off with your head age"
A little side route, but its why certain privacy reaching laws, re important, human rights laws, data protection laws, computer misuse laws, consumer laws. People forget about them, but in this day and age they are part of the barriers stopping out data being misused.