The addition of races like TdU, Beijing, Canada etc to the WT is to broaden the appeal of cycling (as part of its globalization) to both more people internationally, but also to more internationally focused sponsors. 'New' cycling nations (Aust, US, Canada) also provide significant revenue to bike industry companies - including the traditional European companies - and also offer more potential for growth.
Personally I see this as a good thing for cycling as were all team solely reliant on European sponsors, and European governments/local governments for revenue/race support, cycling would be shrinking right now (as we have seen with a number of traditional races being cancelled/shortened etc) due to the ongoing crisis.
By making races like TdU/Beijing WT, and thus forcing the top teams to race, helps grow cyclings footprint and leaves it a stronger sport as a result. Do the riders or fans think TdU is as prestigious as PN, of course not, but its not in the WT because of its prestige, it helps provide a global audience (and to an important market to bicycle manufacturers - over 1m bikes sold in Australia last year, more than cars) and increases the chances of cycling teams - including traditional European teams - attract international sponsors, which is what pays the wages.