According to Builder Magazine:
Several of the most common aging-in-place renovations involve updates to the bathroom, according to the National Association of Home Builders' (NAHB) Eye on Housing blog. More than 80% of respondents in the NAHB's Remodeling Market Index survey reported installing grab bars, higher toilets, and curbless showers. Widening doorways and adding lighting were two other projects more than 50% of remodelers reported as "common" in the past 12 months.
Wet Zone from Narrow House
Even though the underlying motivation seems similar in both cases, walk-in bathtubs have not become nearly as common as curbless showers. Only 12% of remodelers reported installing walk-in tubs in 2018, and only two of the 14 projects on the aging-in-place list were cited less often: lowering kitchen cabinets and countertops.
When NAHB began asking aging-in-place remodeling questions in 2004, curbless showers were about as common as wider doorways. But over the years, the share of NAHB remodelers installing curbless showers has grown, from 54% to 82%. Curbless showers are now nearly as common as higher toilets—even though the percentage of remodelers installing higher toilets also reached an all-time high of 85% in 2018, up from 68% in 2004.