Bonded kiln labourers are one thing, but there are also a lot of bonded land labourers.
Were there any opportunity to make money with labour, things would've changed. See, now if those people were to run away, even then they would have little opportunities to make money elsewhere.
Country is knee deep in trade and financial sanctions around the world thanks to India (try sending a wire there from a Western nation, and you will be up for an amazing adventure.) That's not the only impediment to doing exports.
You have to add to this that the elites there a very conscious that if the industrialisation will "hit the fan" it will hit the fan on them. Some are working quite actively to lobby against industrialisation, and trying to sabotage it with passive-aggressive style resistance.