A lot of people from conservative areas feel like and complain that californians come in and change the "culture" of a place. A lot of times this is the usual dog whistle nonsense and conservatives being mad that liberals exist and california is heralded as some beacon of socialism and liberalism and is therefore the enemy.
On the less politically dumb side of things this can also manifest as gentrification. Wealthier yuppier people coming into a low cost of living town or city and with their money and new population comes a change in whats available. Personally a lot of the low cost of living america are declining rust belt cities and low cost of living due to decades of population loss or stagnation so I dont think this is as bad as people believe.
But gentrification impacts housing prices and it is frustrating for people who lived through the rustier times of a city only to be priced out of homeownerships because the market now includes bidding wars where people from wealthier cities dont realize their overpaying for a property because its still hundreds of thousands of dollars less than it would be back home. Current homeowners get a fun surprise when their taxes are reassessed and their 120k home is now worth 350k and taxed appropriately. Likewise longterm renters notice the uptick in rent as people move in.
Of course a lot of this is a market problem and a supply problem, and a rental protection problem and even if the city were to have just started growing without help from rich californians and new yorkers prices would still go up. But the new migrants are the target and depending on where you live thats california in other places its new york. Still others its both and then some.
And if you're doing alright for yourself or scraping by in your rusty city you may not want things to change even if it means more restaurants, and developments, and things to do. The saying about strong tides raising all sails is not true, some people wind up underwater and drown.