I think you're mixing up different issues.
The RNLI s an humanitarian charity and does a great job.
The potential migrants are participating in an illegal activity.
They set out hoping / intending to evade detection
I think you’ve over simplified it. There’s a world of difference between an economic migrant and an asylum seeker. And buying a ticket requires an individual to give their passport/visa details. In that way, the only way to make the journey is illegally, irrespective of status.
A genuine asylum seeker, rock solid in the evidence that can support their case will, in all probability, hand themselves in. If they don’t do it within a reasonable timeframe they jeopardise their case. Even then, only 40% of applications are approved.
The U.K. pay millions to France, increased by £54m last week, for them to address the issue on their side of the channel. Why does the French Coast Guard shepherd them out of their waters? Because they’ve been told not to do more than that if the migrants resist arrest, and resisting violently is on the increase. Why do the RNLI get involved? Because by international law they have to. Officials on both sides are doing the right thing. And the immigrants know how to play the system.