[steveh]

It's all about the 'second screen' now and use of traditional text services on TVs is shrinking.

Apps cost money to develop and it can be hard to make a business case for minority proprietary platforms. Browsers are incredibly complicated so you'd be developing something that may have issues with many sites, will probably not perform well due insufficient processor and memory on the TiVo boxes and a sluggish UI layer, and will only be used by a small minority of users.