As an experienced contractor, I can tell you that it is crucial to use tile spacers when laying floor tiles. Spacers are small plastic or rubber pieces that are used to maintain consistent spacing between tiles during installation.

First and foremost, using spacers ensures straight lines between tiles. Without spacers, it can be difficult to keep the tiles aligned correctly, leading to an uneven appearance. Moreover, without adequate spacing, there may be uneven gaps between the tiles, which can cause them to crack or shift over time.

Second, using spacers allows enough room for the tiles to expand and contract. As temperature and humidity levels change, tiles can expand or contract, and without enough space, they may buckle or break.

Some people argue that using tight joints with no spacers creates a seamless look, but this method is not recommended as it is hard to ensure uniformity in tile size and shape. Additionally, when installing large format tiles, it is even more important to use spacers to avoid lippage or unevenness.

In conclusion, using tile spacers when laying floor tiles is highly recommended to ensure a professional finish, prevent cracking or shifting, and allow for expansion and contraction. It's worth noting that different types of tiles require different spacer sizes, and it's always best to follow the manufacturer's recommendations for your specific tile installation. As an experienced contractor, I strongly advise you to always use tile spacers when installing floor tiles.