"Not been a problem for most current property owners who buy to suit their budget and then upgrade a the appropriate time."
Most current owners don't usually impact the market (except to the point that a lack of sellers can underpin prices), it is the 'relative few' who speculate, buy at levels that don't suit their budget or their budgets expectantly change that has the most impact on market conditions/trajectory. When they are forced to sell..and the market gets flooded, the drop in price or value impacts everyone's property prices/values. Even if you hold, your property's price/value will have been impacted, you just haven't 'realize' the impact.
