Wikipedia:I don't see why not
Whenever there is a proposal, there is bound to be someone who says, Support. I don't see why not. Others will say Oppose. I don't see why. While both may not be reasons themselves, a lot of users use them as a kind of argument. But are they appropriate?
I don't see why not
Editors often perceive only the good points of a proposal/nomination, and do not see the bad ones. As a result, they may end up supporting proposals with stereotypes or anything of that sort without even knowing it. Or there may be other problems to make the proposal impossible to be performed. Then, someone might come round and, seeing all these bland supports, close it per WP:SNOW, and there we go — another bad proposal passed through.
What these supporters need to do is remain neutral until someone points out a flaw in the proposal. They can always watch the page. If, after a period of time which they deem significant, there is still no objection, then OK, support it.
While some may argue that this method of expressing opinions may result in a whole bunch of neutrals. In fact, as long as the supporters can convince the neutrals to support the idea, this problem would then be solved and the proposal would succeed. If the proposal contains a flaw, then the neutrals, which are more likely to switch to oppose, would be convinced by the opposers, and the proposal is declined. What can be better than that?
I don't see why
Sometimes, Wikipedians may oppose a proposal simply because they don't see why it would help. Although it is not a strong argument, it is a good reason to oppose at places such as WT:WPWPA and WP:VPR. This is because, in these places, useless things must be avoided. However, in places like WP:MOTD, even useless things might sometimes be utilised because it has to be updated every day.
Sometimes, editors may want to act as the devil's advocate and therefore try to split hairs in order to get the nom or supporters thinking. This is indeed a good practice because it will work the proposal/nomination to perfection. On the other hand, an oppose, especially if you forget to change it when all your issues are resolved, may be an obstacle to success for the nomination so instead of using the Oppose tag, you should use Comment or even Support, but....
In addition, newbies may consider it a bite if you oppose something just to play the devil's advocate, so be careful!