I think there is a high potential for 'crossover' if a reviewer becomes successful enough to attract a large following, but to sell out you first must have something worth buying which, for a successful reviewer it means a reputation earned through years of work to raise their profile/financial support via patreon etc. If you get a reputation for selling out you stand to piss it all away. Who gives a shit about Rip/Superdad today? and Zophie Vapes, Indoor Smokers if they're still around
In the case of a fledgling reviewer, or someone who has 'only' a few thousand followers (which can also take several year to gain) I don't see any point - they won't have the clout to demand much in the way of a fee, they may get free product for review but what kind of enticement to sell out is that to someone who already has loads of gear? Getting a couple of mainstream kits/pod systems and a shit load of disposables only gives them more product (that they may have no real interest in) to review, but it doesn't have much resale value.
A reviewer becomes an influencer when they guarantee a good review for payment.
Some may sell out, but hopefully the readers/viewers are adults who realise they are only getting someone else's opinion, that they may or may not share, and can come to their own conclusions.