If the purpose of vote buying is to increase the visibility to your post, making it to the trending page and increasing the chances of better engagement from the community then bidding for a vote or vote buying process within the community is always a win win situation. Because the primary purpose for an author is to have better readers and for that the post or blog should be visible to the audience within this community and in that sense vote buying really helps. I do consider increasing reputation as secondary kind of thing to a true blogger. The content creation is something needs proof of brain and needs to be presented in a better way so that the readers will feel good and at the end the reader must read it and engage with the content productively. In order to help an author in this aspect the vote buying system has been designed in this community, because the ranking of the post is generally aligned in terms of what the earning it shows.
If someone is looking to make ROI or reveneue out of the vote buying facility available in this community, then I personally see it as an abuse to the existing system. This is not what this community is up to. Although some people are trying every way out to make an ROI from the vote buying facility, but that is against the spirit of this community and many times it has been debated upon within this community and from time time the vote seller has come up with strict guidelines so that abuse to vote buying can be minimized.
As per the principles and the fundamentals of the community we all should encourage good content and healthy engagement and if that can be possible by promotional tool like "vote buying", then we must use that in that way and within our individual capacity we should not abuse the vote buying facility. If we will be disciplined in that regard then ultimately this community will evolve out as a strong and spirited community.
Buying of votes with the use of bots actually depends on what you intend to use it for. Just as you've stated in your question, some people buy vote to increase their steemit reputation, while some may buy it to increase their posts popularity (making it more visible to appear on the trending page).
Is it a win or lost?
It can actually be a win for you if it it enables you to achieve your aim or goal. Not everyone who buys bot votes actually achieve their aim and in this case, it will be a loss for them.
Some people also buy vote bots for the sake of business(trading/investment). These type of people are more concerned about the price of steem such that they intend to use their earned Fiat currency to buy steem with the use of vote bots since they will earn more steem and it can also add more to their reputation on the platform.
In conclusion, there is more to the buying of vote bots other than increasing one's reputation and post popularity. It can also be a win and loss.
Thanks for reading and I hope this helps.