Remember that there is talk of the EU imposing punitive tariffs anyway as punishment for the temerity of choosing to leave the EU.

In a situation where EU representatives have (in some cases quite openly) said, "We are going to make this process as painful as possible." It's certainly useful for the UK to have as much ammunition is possible going into these negotiations.

The UK is able to say to the EU, "Depending on the outcome of these negotiations, we may or may not withhold over 12% of your operating budget." That kind of implicit threat tends to make an organisation more amenable to good-faith negotiation.

That's why it was so important to strike down the two amendments made to this bill. If the rights of EU citizens to remain in the UK were pre-assured, and parliament was allowed to overturn the result of the referendum in the case of a bad deal, the EU would have drafted the most punitive measures and refused to negotiate.

Now that those amendments are gone, and the UK could potentially withhold a decent chunk of money, they should play a little more nicely.