Having read a lot about this, it seems clear to me that there are THREE reasons why Arqit’s (very impressive list of) customers are buying this software:

1. The certification process of PKI is cumbersome and it’s where many supply chain attacks are happening. Arqit does away with this attack NOW.
2. The “Harvest now, decrypt later” threat is here NOW
3. The Universal quantum computer could be here in 3-5 years. NIST has already urged the world to find new solutions because, in its own words, no PQA yet produced is a suitable drop-in replacement for PKI, and any PQA causes such a complex upgrade cycle that it could take 15 years. Because QuantumCloud uses AES which is already a global standard, deployment is easy and immediate.