It is the SGPC sikhi that rejects Baba Sri Chand. Traditional sikh and Guru Sahibs had a lot of respect for Baba Sri Chand and the Udasi sampradaiye.
Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/sikh-sikhi-sikhism/38380-baba-sri-chand-and-sikhism.html
Udasi sikhs are the sadhus of the sikhs and spread dharam to far away places, so really they brought the most people to the sikh panth thinking.
The Udasis along with Nihang Singhs were put in charge of the Gurdwaras by Guru Gobind Singh as well. Also one of the Gurus gace his son Baba Gurditta ji to lead the Udasis.
Baba Sri Dhan;'s sampradaiye has had a great role in sikhi and it is one of the 4 major sampradaiye in the sikh panth. However in SGPC sikhi, the pretty new jathebandis are recognised more than the traditional sampradaiye, such is the state of sikh panth at present.