I think that makes sense in the context of the whole sentence: > Who can stop people from utilizing device spoofing if a website cannot show captcha to mobile

I think that makes sense in the context of the whole sentence: > Who can stop people from utilizing device spoofing if a website cannot show captcha to mobile devices even if some rate limits are exceeded, or if a company offers specific discounts or products only to some types of devices? The "cannot" is not meant in technical, but rather organizational sense - somebody decided that they don't want to show captcha to mobile users ( one reason might be that the user experience was deemed too bad). The same way they decided to offer specific discounts only to some other class of device.