This I agree with you, it should advocate for the redistribution of wealth, but what happens the vast majority of occasions is that left wing people/parties only advocate for increase in government spending which usually comes from debt or money printing. You basically condemn a whole generation to pay the debt over money you borrow/print today in the hopes that this money will bring social justice or increase economic growth and employment.
Funny thing is, nothing creates more inequality than governments doing it. Just compare a curve of inequality with the curve of money supply. It's not rocket science. All this money created along with negative interest rates ends up in the hands of big institutions and rich people, which then inflates heavily assets across the markets. Then young people can't buy houses anymore, assets are so inflated that it creates bubbles in the stock market with companies being valuated by unreal multipliers.
There is a saying that goes like: the right (from economics point of view) is the best to make the cake grow, but don't know how (or want to) to distribute the cake. The left is the best to distribute the cake, but don't know how to make it grow.
I wish the left could be less delusional and more focused on how to distribute the wealth but in a responsible way. Although to be honest the world has gone 100% crazy and even the right became huge irresponsible spenders.
In the United States at least, both parties tend to emphasize spending on the things they value over cutting the spending of things they don't. This isn't a uniquely leftist phenomenon, this is a political phenomenon. It is easier to spend than it is to cut.
That said, there are a lot of arguments right now about whether the debt level currently sustained by the US is a bad thing. It simply hasn't had the negative consequences that traditional wisdom believed it would, so at this time, it seems, especially with how low interest rates are, that spending doesn't really have a strong drawback.
I also don't really agree with the idea that government spending necessarily increases wealth inequality. It obviously should depend on how this money is spent.