Altcoins are taking benefit of the doubt and also benefiting from the popularity of Bitcoin They are rising in value because Bitcoin is.I am not saying every altcoin is dependent on Bitcoin,some altcoins do have unique features that Bitcoin doesn't and that helps them in adoption amount people.More and more people are getting aware of crypto currencies via media,bitcoin price hike etc and people believe alts are in early stages and they will be big someday like Bitcoin so people invest in their favorite altcoin