If you block marketing from using the tools they want, they will do it anyway but using personal email addresses like Gmail or something like that especially with the generous free tiers.
Shouldn't people just be able to try out new things? How can a company be innovative otherwise? And at a specific point (e.g. putting customer data into it), they need to start a proper vendor assessment process.
It's always a balance of information security awareness, culture and technological solutions within an organisation.