You're talking about economics.
Not just economics. Who's going to take care of all those old people? In the west currently (including the US and Canada) birth rates are at below replacement level. In Canada it's 1.6 and dropping. If Canada doesn't import people (via migration) then the population will be declining as of now.
Thanks to modern technology and medicine, people live longer than ever and the kicker is, that while they live longer than ever, they never live and die like before, now it's a very protracted and prolonged decline that uses many many resources. Why did old governments set the retirement age at 65? Because few people lived that long 50 years ago.
By the time my kids are established adults in about 30 years, people over 65 will be the majority. There won't be enough people to take care of the elderly. We're going to definitely need robots.
Everyone else here is talking about the planet- which has finite resources.
Traditional economics relies on growth, growth that increases year after year. In nature the only things that do that are cancers, plagues, and pandemics. All things that result in a catastrophic collapse.
I love nihilistic and pessimistic people.
I'm not aware of a single thing yet that we had to stop doing because we ran out of something on earth (except helium) and we couldn't find an alternative (resource or method). For every thing the market manages to find a solution. Market economics provide the incentives and human ingenuity finds the way. When something becomes scarce enough, its price rises enough to give people enough incentive to find an alternative resource or way to do things.
Nihilists don't think in this way. They think that (for example) we're running out of copper. Humans will extract every last copper ounce from earth and sell it at $1 per kilo like a long time ago, and when we can't find anymore, we'll just throw our hands in the airs and sigh and say 'We're done, no more copper' and give up.
It doesn't work that way.
Copper is getting rarer. Its price is going up quite a bit, people are conserving it for the most important things and starting to find and reuse what we've used and discarded; and many of the things we used copper for previously we're now using other material after we've done our research.
When China blocked the export of rare earths in 2011 their price spiked high enough that people went really looking somewhere else and found it. Japan found enough rare earths at the bottom of the ocean to last over 800 years at current consumption levels.
Materials that don't evaporate into space like helium remain on earth and when there is enough need, people find a way to reuse whatever was consumed.
Did you know that today humans plant 10% less land than in the 60s despite the population expansion?
Do you know what the solution to global warming will eventually be? It's the opposite of what you think. It's more grazing animals. You can laugh. Go ahead, I know you will, but it's true.
Grazing animals in large herds help sequester a lot of carbon in the soil as grass roots. Look it up. You know what, I know you won't look it up. I've done it for you:
Watch the video.
Do you really think that western governments would have a problem keeping unwanted migrants out if they didn't want them? They really really want those migrants and they only talk against it to save face with the portion of the population that is against it.