Look into the concept of inbound liquidity...

In short, if you open a channel yourself, all sats will be on your side of the channel. You can thus transfer sats from your channel to someone else's. However, as a business for instance, more often than not, you want people to be able to send sats to you. For that, you need channels where the sats are on the other side of the channel, i.e. in-bound liquidity...