The ipad was originally designed and still defaulted to be a portable portal to iTunes content. It was meant to be used by adults - which is why it’s designed for a single user with an Apple ID. And as with many app developers, the presumption is that purchases will be made. Which is one reason many apps encourage you to give them a payment method ‘just in case’. That is a common thing anymore.
The burden is on the users to understand the tech they use and how to use the tools provided to lock out or enable features as they wish.
Screen Time is a recent addition to the device in response to the growing number of parents that choose to purchase an iDevice and give it to their children. iPads are not the only choice. There are many kinds of tablets out there, some geared totally towards kids, others not. It’s up to the consumer to do their research and make the purchase that best serves their needs. It’s also on the consumer to do their research and read manuals etc to fully understand the tech they are using.
I won’t comment as to whether it’s good or bad to have things defaulted to on or off, largely because, at the end of the day, we’re just users like you. We have ZERO power over anything apple does. Many participants here have spent years learning the ins and outs of devices and choose to share that knowledge with others.
You may have a valid point about what should or should not be defaulted to on, but this is not the correct place to share that. You’re basically shouting into the wind. Using the feedback link that has been provided is the best way to share your thoughts and concerns with Apple. All feedback is read and logged and if Apple will choose to change their mind about defaults it will come from logged issues, not forum posts. (In other words, make the feedback and give them the numbers to encourage them to rethink defaults)