To many people (not really versed in internet culture) that would be pronounced [pawn/porn]tube, with the connotations such a name brings.
"Mom can I go on pwntube to get a video for my homework?" "WHAT?!?! PORNTUBE!?!? NO!!!"
;)
"Mom can I go on pwntube to get a video for my homework?" "WHAT?!?! PORNTUBE!?!? NO!!!"
;)
Those who want their sites/products to go mainstream without ridicule (ExpertSexChange.com/ExpertsExchange.com is a popular example) or false negative impression/bias. This is why people often spend a lot of time to choose a name carefully, especially when you consider the long-term branding and marketing.