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Those popups were so prolific that all browser developers responded by implementing popup blockers.
Which kind of led to the absolute mess of banner ads (and the adblockers created in response) that we still have today. I dare you to deactivate your adblocker on any of the major (commercial) news sites.
I also recall not a single one of those builtin popup blockers working as intended, random popups would show up anyway. Hell, that feature still leads to annoyances when a site actually needs to open a new window (happens with some internal systems being used where I work)