1) AI startups usually don't have a lot of value to potential acquirers based on their data, but based on other things (e.g., talent, customers, business model, platform, brand). That's like saying you shouldn't use AWS because Amazon can just steal and commercialize all your data.
2) There are other companies than Google that acquire startups
Having said that, I highly doubt that Google can just use all the training data to on GCloud to launch their own products with that. They can surely look at it and maybe do stuff with them internally, but I am pretty sure that they can't use them commercially.