Exactly.
Plus with your use case there may be other criteria, for instance, if you have an 'apply now' job application form you can take in other data such as how long it took for someone to fill in the form and where their IP address is.
If you are hiring for a job in London and you are not likely to hire the office manager from Timbuktu who spends less than ten seconds uploading their CV and writing some cover letter then you can make your backend form processing not forward that email on to the HR department.
Putting a timestamp in the form as a form field with it encoded is easy. On the submit side you can unencode it and come to some judgement on the matter.
There is also the hidden checkbox with 'hideit' set to 1, not sure why that works but it does with a form you have written yourself, i.e. not stock Wordpress.
Although we don't like Google doing their deep-stalking of the visitors, fingerprinting them in re-captcha, there is no harm in collecting a little bit about the user. The user agent, screen size and location is useful in a sales/support perspective. If someone has a posh computer that says something about them. If they are using an old copy of a Microsoft browser then that says something about them.
On a general forum there can be standards of English to enforce. If someone is not using capital letters to start sentences, not using punctuation and not spelling so well then that can be flagged before they hit the 'send' button.
I have done a lot of tidying up of email lists created by bots and what surprises me is how easy it is to spot the fakes. It is like the bad guys in movies and games, doing everything possible to make it easy to get 'em. If spammers did real world robbery they would carry a bag labelled 'swag', be wearing 'Groucho glasses' and a stripey jumper.