This has happened to me a few times in various African airports and once in Mumbai. They can be a nuisance but in fairness for about $10 they will whisk you past all the queues and take you through the VIP/Diplomatic passport and security checks.
On arrival it’s the same but they will take your tags, get your bags, find a porter (if needed) and a half decent taxi that does not rip you off if you are not being collected.
It’s well worth $10 and I tell them what they will get but only pay when you are in the lounge / taxi.
I guess BA does not shoo them away since if BA offer the service they have to pay to use Fast Track, for the assistance etc. This way the customer is happy and they save a few Rupees or whatever.