Casting shadow on their backyard. Bringing noise to their street. Ultimately, lowering the value of their property.
The key problem of US housing is that a house is seen as an investment vehicle, which should appreciate, or at least appreciate no slower than inflation. Keeping prices high and rising can't but go hand in hand with keeping supply scarce.
Is this regularly true? IME, in Northern VA, land values have always increased with infill development. Thinking specifically of Arlington in the Courthouse/Ballston/Clarendon strip in the 90s and 00s. And now Reston.
Traffic and noise concerns might be legitimate, but I'm not buying the loss of value argument.
Is it always true? More than once I heard fears about undesirables moving in, crime rate growing, the neighborhood "losing its character" that commands the high prices, etc. The resistance is real at some places.
The land value argument is downstream of the real issues - some people don't want change and fight it.
If it was purely a money question you could just get some billionaire to go around buying out entire neighborhoods, redeveloping them, and turning around and selling them off for a profit (because they'd be worth more, right?) - the fact that this is not being done either means there's a great new startup or there are other issues.
The key problem of US housing is that a house is seen as an investment vehicle, which should appreciate, or at least appreciate no slower than inflation. Keeping prices high and rising can't but go hand in hand with keeping supply scarce.