I can't speak to Broadcom's motivations, but the end result has certainly been that they are the least open source-friendly WiFi vendor, behind Qualcomm-Atheros

I can't speak to Broadcom's motivations, but the end result has certainly been that they are the least open source-friendly WiFi vendor, behind Qualcomm-Atheros, Mediatek, Marvell and Intel (client only). When Linksys wanted to do a successor to the WRT54 series trading on its open source reputation, Broadcom wasn't an option because they've made themselves the NVIDIA of WiFi.