Comment by holowoodman

Weather stations do usually come with a calibration problem: If you are on the sunny side of your garden, temperatures will be higher. If you are above concrete, temperatures will be higher, above grass, lower. Height matters. Wind and shielding from wind matters. Same for most of the other sensors, data is easily skewed by location, color, size, height and ventilation of the housing.

Therefore for comparable, calibrated data for real meteorological use, there are standards (unfortunately national, so there might be differences in some places) for all the above. The sensor housing has to be white, provide shade and total rain protection, but well-ventilated by grills on all sides. It has to be mounted above a patch of lawn of at least 10x10m, no shade, no significant nearby wind barriers, at a height of 1.2m. All sensors have to be at least 10cm from the internal walls of the housing.

If you don't care about strictly calibrated scientific data to use in your weather model, of course a simpler device will do. Also, nowadays, it is possible to account for deviations of certain stations due to the aforementioned factors.

Another factor is also serviceability. A cramped tiny housing that is hard to open and inspect isn't ideal when you have people touring the country servicing weather stations all year.