> you will lose a lot of people who would learn about it later
Can't lose something I don't have.
> isn't it better, if only because of the network effects, that they use free software, even if only for part of their needs
For themselves, yes, it's better. For the Free Software movement, I'd say it isn't: if they're taught that short-term practical reasons are the reason to try Free Software, that will also get them away from software freedom when short-term practical advantages are present in non-Free Software. If they're taught that sacrificing their freedoms is ok, that's what they will do when offered bait that shines of short-term practical reasons. I.e., just when we'd most need them to stand firm with us for software freedom, they'd detract, because they haven't got the right message.
It is true that a few of those who start by learning the short-erm practical advantages will see through that and find out about the deeper, long-term practical and ethical reasons. But a majority doesn't. And when the majority doesn't stand for our values, our whole community is vulnerable: we lose, because the network effects, instead of favoring our goals of eliminating the non-Free Software oppression, play against them.
I wish I was just pessimistic, but a social experiment started in 1998 shows just how perverse that is. A group you might be familiar with launched a campaign to promote Free Software on its short-term practical benefits, leaving ethical values out of the picture. It got very popular, and the result is that a lot of software those who subscribe to that ideology produce is not quite Free, and many of them will attack and ridicule those who stand for software freedom.
I'd much rather the Free Software movement had grown slowly but surely, just not as slowly as it does now because of the detrimental effects of that campaign.