Do all the ad companies require this pixel on every page of your site? In other words, could you not have an ad platform specific page that embeds the pixel and acts as the landing page for any of your ads?
If so, I don't see any problem with that. The only customers accessing that page would be incoming ad clicks.
No. They don't even require it at all, but they encourage you to do so to get access to certain things.
Without the pixel, the platform sees a click on their side. But if you wanted to pay for other conversions, eg a purchase, you'd need to send an event back (either via pixel or via API).
As an other example, if you wanted to retarget, you'd also need the pixel. Let's say you wanted to target users who added an item to their cart but never purchased, the pixel would fire a "added to cart" event.
Finally, if you want look-alike audiences, you'd want to pixel as many users as broadly across your site as possible. As an example of this last one, you might want to tell the ad platform to show your ad to people who seem to resemble people who have made purchases on your site. Having the pixel let's them build that list of users who purchased on your site, then try to target users who seem to have similar interests/location/browsing habits. The funny part about this is the platform might implicit learn to target your ad to people who have visited a competitor. But since you add the pixel too, they show the competitor ad to people who visit you. So the ad platform is really a weapons dealer here.
So Yea, you could decide to only use the pixel in a limited way, or not use it at all, but you'd miss out on better targeting, optimization, and reporting.
If so, I don't see any problem with that. The only customers accessing that page would be incoming ad clicks.