I came across this rather hilarious reason that supposedly clinched the classical status deal for Malayalam.
Anyway,drab I don't see any reason for not giving classical status to Tulu.
Mahadevan’s intervention on the Edakkal engraving was decisive in a way. He proffered the reading ‘pazhama’, meaning ‘antiquity’ in Tamil and Malayalam. Coincidentally, just about then, Kerala had set up an experts’ panel to make a case for classical status. Besides litterateurs like O.N.V. Kurup, it included linguist Naduvattom Gopalakrishnan. Now, he had just what he wanted. Zeroing in on ‘pazhama’, he extended it, saying the prefixed string was not ‘Sree’ but the Malayalam ‘Ee’ (‘this’). Most advocated caution, Varier even called it a “dangerous interpretation”. But who was to argue against the tide of provisionist history! If you’re looking to prove your antiquity, what could be more fortuitous than to come across a petroglyph that proclaims, precisely, “O! This Antiquity” and putatively joins you to Indus cultures? It’s almost pluperfect: a past that talks of an older past. One neat standing jump on an Indus Valley zebu over the 1,500-year cutoff.In fact, the author of the article mentions Tulu being left behind. But if Malayalis say 'This Antiquity' and get Rs. 100 crores classical status, Tuluvas can say 'pirak' (archaic/old) and claim the same. In fact, some of the Tulu enthusiasts have observed the origin of the word in the Indus valley region Pirak. Thus Tuluvas are also connected to Indus culture.
Anyway,drab I don't see any reason for not giving classical status to Tulu.