If Shri Ram and Shri Krishna are avatars of Lord Vishnu, why isn’t lord Vishnu worshiped directly?

If Shri Ram and Shri Krishna are avatars of Lord Vishnu, why isn’t lord Vishnu worshiped directly? The other answers have already stated some of the many Vishnu temples which are present. However, it is not only about temple worship, but also the daily worship we perform. Vishnu is the most important deity to be worshipped in Vedic ceremonial rituals and is the foremost of those venerated in the yajna. It is necessary to chant His names in the form of mantras, such as “(pranava) madhavaya namah,” “(pranava) keshavaya namah,” etc. Apart from that, many other rituals in Hindu households, such as the Satyanarayana Katha, Gajendra Moksha, etc., are all related to the four-handed Lord. He is also worshipped during major festivals. Hence, Vishnu is widely worshipped ‘directly’ as well. Thanks! Jaya Bhagavan Hari!