Sri Ramanuja Munaye Namaha,
Sri Velukkudi Krishnan Swami Guruve Namaha,
Dear abhigau Gautam BhagavAta,
It is a great question. However there are some temples in South India for these Mahans/Rishis.
There is Valmiki Temple in Thiruvanmiyur Chennai.
There is Veda Vyasar Tapovanam Temple in Sembakkam near Thambaram Chennai.
There could be Parasarar Maharishi Shrine in Thiruvelliangudi Perumal Temple. There is Parasarar Pushkarani due to the Sthala Puranam.
Also, Swami Alavandar’s one of the wish in HIS last minute before reaching HIS Acharya TiruvAdi was to name the DESERVING DEVOTEES with names of Parasara Maharishi and Veda Vyasar. Swami Alavandar’s wish was accomplished by Swami Ramanujar by Swami Ramanujar naming Swami KoorathAzhvan’s two Deserving Son’s as Parasara Bhattar and Veda Vyasa Bhattar.
In addition to the above, If BhagavAtas question is why Veda Vyasar or Parasara Maharishi or Valmiki Maharishi deities are not popularly seen in ALL the south Indian Sri Vaishnava Temples, except in few places, then we can only derive the reason as below based on our own understanding from upanyasams as below:
Though these great Legends/Rishis preach Spiritualism, they themselves follow Upasana Maargham for Moksham (“Upayem/Route” to Moksham is their Own effort and “Upeyam/Destination” is BhagavAn’s Lotus Feet), which is good Maghma which requires long life like more than 60,000 years or so to follow it correctly like in Krita or Treta Yugham, but difficult to apply in Kali Yugham.
So, the prescribed shortest path to Moksham in this Kali Yugha as per Shastras is Sharanagathy Margham (Upayam & Upeyam both are BhagavAn Lotus Feet which is nothing but the Lineage of Alwar’s/Acharya’s ThiruvAdi).
So, if we keep such Rishis deities in all SriVaishnava Temples, then at some point, we ordinary devotees will have a tendency to follow what they were following for Moksham like Upasana Margham instead of Sharanagathy, and we cannot achieve Moksham in that path in this Kali Yugha due to decreased life span, fluctuating Shraddhai, diluted Acharam/Anushtanam. So, our PoorvAcharyas like Swami Ramanujar Honors them in the Spiritual teachings/Granthams etc only… but our PoorvAcharyas may not have entertained having their deities in Temples except in few places, Instead we have Deities of Alwars and Acharyas Popularly in all SriVaishnava Temples just for our benefit to narrow our Thinking and Focus on Sharanagathy Margham, so we could reach Moksham in SAME BIRTH by saying “Srimathe Ramanujaya Namaha” as Gauranteed by NamPerumal (SriRama) in Sharanagathy Gadhyam.
No Hassles….No Worries…..
Adiyen Sri Velukkudi Krishna Dasan,
UYYA ORAEY VAZHI UDAYAVAR THIRUVADI,
Sarvam SriKrishnarpanam Asthu