Assuming all other customer service aspects are equal? Yes, I'm absolutely more likely to order more from a company that provides samples than one that doesn't.
I currently order on the regular from three
juice vendors. All three have juices that either I or my fiance enjoy. They all have a similar per ml price point on their smallest size juice packages (under $0.50 / ml).
The first provides a "sample" (read: free bottle & you can choose it) with any order over $15. They offer many customizations on their juices. They give SIGNIFICANT discounts for larger sized bottles. They also have excellent customer service, are quick to respond to emails & their forum threads, and if you get something that seems off in any way, they bend over backwards to remedy it. They get approximately 75% of my juice budget.
The second does not provide samples. They ship quickly. They are quick to respond to emails & forum threads. They are willing to customize juices to your taste (even if they don't explicitly say that on their website). When I pointed out a problem with their website, they gave me a free 10ml bottle of the juice I was trying to order the next time I placed an order (which was as soon as the problem was corrected on their end). They get about 20% of my juice budget - they're a very new vendor, and as they continue to expand their selection of flavors, it's likely to be more.
The final vendor does not give samples, takes longer to ship than I really care to wait. They do offer significant customization options, although some aren't well explained. They're terrible about updating their webpage (I've seen their "flavors of the week" be the same for 2 - 3 weeks, and they advertise a coupon code that expired weeks ago). I really haven't been terribly impressed with anything, except they have one really really good juice. They get about 5% of my juice budget, and I don't see that increasing anytime soon.
So, I guess - for me - I will reorder from someone if they have at least one outstanding juice (that I've tried), but I'm more interested in being a repeat customer somewhere where the service is amazing, and they're willing to work with me to get juices that *I* want, instead of what they want to offer me. But price is important too; and samples do - in my mind - figure into that. A free bottle of juice - especially when I can request pg/vg ratio, nic level, and even FLAVOR - makes the entire purchase a better value. I am sure there's many boutique vendors that have great service, offer samples, and have good juices - I'm just not willing to spend the price per ml it requires to "try out" their juices.
TL-DR - Samples absolutely matter. Other things just matter more.