When land rent goes into private pockets, neither labor nor capital get their fair returns (wages and interest).  The true entrepreneur (as opposed to the one whose business is mostly collecting land rent) makes out just as badly as the individual who supplies his labor to that entrepreneur.   Meanwhile, the land speculator, the private rent collector hides behind the widow's skirts.  Business plans are never executed, or businesses fail, and a new category of people comes to prominence: the working poor.  Where land is available, there is little poverty.  Where land's price is high, many more people lack sufficient income to provide for their own and their families' needs.  Consider this fact as you think of both American poverty and global poverty.

When people must "invest" large amounts in money in land (whether to rent it from a landlord or to buy it from a seller), they have little left for machinery or equipment (capital) or employees (wages) — or, as homeowners, to build a house and furnish it. Buying land doesn't create jobs for anyone except perhaps real estate brokers and mortgage lenders. Buying machinery and household goods creates jobs. Building homes creates jobs.

H.G Brown: Significant Paragraphs from Henry George's Progress & Poverty, Chapter 8: Why a Land-Value Tax is Better than an Equal Tax on All Property (in the unabridged P&P: Book VIII: Application of the Remedy — Chapter 3: The proposition tried by the canons of taxation)

The ground upon which the equal taxation of all species of property is commonly insisted upon is that it is equally protected by the state. The basis of this idea is evidently that the enjoyment of property is made possible by the state — that there is a value created and maintained by the community, which is justly called upon to meet community expenses. Now, of what values is this true? Only of the value of land. This is a value that does not arise until a community is formed, and that, unlike other values, grows with the growth of the community. It exists only as the community exists. Scatter again the largest community, and land, now so valuable, would have no value at all. With every increase of population the value of land rises; with every decrease it falls. This is true of nothing else save of things which, like the ownership of land, are in their nature monopolies.

The tax upon land values is, therefore, the most just and equal of all taxes.

• It falls only upon those who receive from society a peculiar and valuable benefit, and upon them in proportion to the benefit they receive.
• It is the taking by the community, for the use of the community, of that value which is the creation of the community.
• It is the application of the common property to common uses.

When all rent is taken by taxation for the needs of the community, then will the equality ordained by Nature be attained. No citizen will have an advantage over any other citizen save as is given by his industry, skill, and intelligence; and each will obtain what he fairly earns. Then, but not till then, will labor get its full reward, and capital its natural return. ... read the whole chapter

The Most Rev. Dr Thomas Nulty, Roman Catholic Bishop of Meath (Ireland): Back to the Land (1881) 

It never occurs to either side that a third party could possibly be liable to blame. I think I have shown that neither party has received, or at all events can retain for his own use and enjoyment, its fair share of their common earnings. The existing system of Land Tenure, like a great national thief, robs both parties of an enormous amount of their earnings for the benefit of a class who do not labour at all.

As the operatives complain the louder, so the case they make against the capitalists seem really the weaker and the worse founded of the two. Mr. Cairnes, with many others, proved to evidence that unless in rare and exceptional cases it is perfectly impossible for the capitalist to withhold from the operatives their fair share in their common earnings.  Read the whole letter