I have no problem whatsoever with a company making money. But here we're talking about a single company in a close to monopoly situation and who uses its position to dictate its rules.

I think you are misremembering here, when blablacar started and was called covoiturage.fr there were a variety of other carpooling websites, some having been around for several years notably covoiturage.com.
At the time carpooling through websites was on the rise and many competitors existed (123envoiture.com, easycovoiturage.com, vadrouille-covoiturage.com, and more), all were free to use. I remember because I was an active user of pretty much all of those sites. covoiturage was one website among others and not the most popular, then came Frédéric Mazzella who bought covoiturage.fr and create a company Comuto to operate it with the intent of aggressively capturing the carpooling market.

first step was to offer the service for free and build a community around it while buying the competitors, next step was to push the remaining competitors out of business with the network effect and use the fear card to position blablacar as a unavoidable middleman (so people could not communicate directly and strike a deal outside the website as was the usage until that point), then pivot from free to paid for.
Last step is domination of the market and increasing prices to very expensive as there is no competition as Mazella explained in an interview:

"Pour l'instant, seul les services Français et Espagnol sont payant, pourquoi ne pas toujours commencer avec le modèle économique ?", Kevin Deniau.

"Tout est un problème de masse critique et d'absence d'offre de covoiturage", Frédéric Mazella.

F.Mazella n'a pas souhaité dire que le passage en mode gratuit de Blablacar est uniquement pour capter l'attention des utilisateurs et qu'une fois le marché écrasé et dominé sous couvert de gratuité, le système payant se mettait en place. Ce fut le cas en France de manière progressive pour faire passer la pilule et c'est la même chose en Espagne, où la fronde s'organise petit à petit.
https://blogs.mediapart.fr/evenstrood/blog/110714/covoiturag...

I'm not saying anything about bad practice (good or bad is a relative notion), I'm saying that blablacar destroyed the social component of carpooling to turn it into an economic one. That blablacar put artificial barrier preventing people who need carpooling the most (people who cannot afford a smartphone or a credit card) from having access to it.

I've been doing carpooling for years and had no issues with cash payment or direct contact with other users, but suddenly blablacar marketed these as undesireable and risky and pretended there was a need to move to less freedom for more security by making them the unavoidable middleman and upfront payment, obviously the need was actually on their side and was about putting them in position to maximize profit.

And I'm not alone to have noticed this, this is quite common knowledge [1][2][3][4][5]. It's around that time that I notice a change in carpoolers, before all were people going from one place to another, now appeared people with no need to go from A to B with large vehicles taking as much passengers as possible to make as much money as possible.

You may think this is win-win situation, but it's really not[7] (also the testimony at the end of [2]), it's a business as usual situation where capitalist parasitic company turning something desireable into an economic commodity/convenience [8][9]

we'll have to agree to disagree on me despising blablacar for what they did as being misguided. Frédéric Mazella knows well what he did and he dit it on purpose with intent. I do realize how realistic and sad it is that a capitalist company killed the human potential of carpooling to try to meet ROI expectation of those who funded them while aiming for world market domination by his own admission. The social element of being human ought not to be controlled by finance.

I hope that by reading all this including sources, you understand where I'm standing and that I know what I am talking about.

[1]: http://carfree.fr/index.php/2014/07/04/la-finance-a-t-elle-t...
[2]: https://comptoir.org/2015/05/08/blablacar-comment-ils-nous-o...
[3]: https://blogs.mediapart.fr/evenstrood/blog/200614/blablacar-...
[4]: http://alireailleurs.tumblr.com/post/89843872188/blablacar-a...
[5]: http://leplus.nouvelobs.com/contribution/891698-covoiturage-...
[6]: http://simplifier-la-mobilite.tumblr.com/post/112955153091/b...
[7]: https://forum.quechoisir.org/frais-de-covoiturage-non-rembou...
[8]: https://www.monde-diplomatique.fr/2013/10/DENOUN/49720
[9]: https://www.journaldunet.com/management/expert/60567/abus-de...