It would give special interest groups a lot of power. A lot of people are against subsidies in general but for most of them it is not a core issue. Now suppose

It would give special interest groups a lot of power. A lot of people are against subsidies in general but for most of them it is not a core issue. Now suppose there were three issues you had to vote for; subsidies to group A, subsidies to group B, and subsidies to group C. Most people won't care and won't show up for these votes (no one except for politicians have time to vote on hundreds of issues every year). However, a large number of people in group A will vote for subsidies for them, as will people in group B and C.