The City Council of the suburb of Darien recently approved a new apartment complex. The public discussions of the proposal and the discussions of a different apartment proposal in 2021 showed why residents did not want apartments:

Neighbors objected, saying they’d prefer condos to apartments. Some said they feared the apartments would turn into Section 8. Others raised the prospect of crime…
Alderman Joe Kenny said then that the building in question would not be an issue if the developer planned condos instead of apartments…
“I felt some of the comments in the emails came off as really derogatory. The tone in those statements, they came off to be kind of racist, and it promoted a level of classism that Darien is not proud of,” said Vaughan, who was the council’s only African American.
In response, a man stormed out of the room. Others denied that race was a factor.
But race was explicitly mentioned in one of the dozens of comments that the city posted to its website.
Across suburban communities, these two reasons are commonly mentioned in opposition to apartments: (1) who will live in the apartments and (2) preference for condos or other forms of residences that require ownership. Regarding the first, sometimes the language is veiled and sometimes it is not. It sounds like those who opposed apartments in Darien were clear about who they did not want in the community. And that building condos instead would address their concerns.
And what is the answer in suburbs to these concerns? Here is one answer given in Darien:
He said The Jade was a “beautiful building,” occupied by young professionals. An alderman said something similar recently.
To assuage the fears of residents, these reasons are often provided: the new apartments will look high-quality and young professionals will live there. These are intended to show that these apartments will be occupied by people residents will find acceptable in the community.
This is a way that suburban exclusion continues. I have found similar discussions happening for decades for Chicago area suburbs. Another reason sometimes provided by objectors is that apartments will disturb the character of the community. This reason is often related to the two explicitly mentioned above.
Decisions about development are not just about properties and buildings; they are about who community members want in their suburb.