It seems like there's never been a better time to launch a new subscription streaming video service. Streaming hours have exploded this year as people spent more time at home, movie theaters closed, and other entertainment options like sports and concerts were suspended. New services from AT&T's (NYSE:T) WarnerMedia and Comcast's (NASDAQ:CMCS.A) NBCUniversal are joining mainstays like Netflix (NASDAQ:NFLX) and Amazon (NASDAQ:AMZN) as well as Disney's (NYSE:DIS) Hulu and Disney+.

The combination of more time on the couch and more services to watch is expected to propel average time spent watching subscription streaming services over one hour per day this year, according to eMarketer. But growth appears to be going to the well-established services, and it'll be much harder for new competitors to grow going forward. For newer subscription services to succeed, they'll have to take market share from existing services.

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Image source: Getty Images.

The big are getting bigger

Subscription streaming is dominated by four services: Netflix, Amazon, Hulu, and Disney+. Netflix and Hulu have been streaming video for over a decade, and Amazon is only a few months away from reaching that 10-year milestone. 

Disney+'s sudden race up the charts can be owed to its strong brand and simple messaging. But its launch may be an exception rather than the rule. Several other services without the same strong brand and messaging have launched over the last eight months without the same response, namely Apple TV+ and Quibi.

HBO Max's message to consumers is simple at its core -- same price, twice the content -- but its rollout to consumers has been a mess. It has multiple apps in limbo and still doesn't support the major connected-TV platforms. Meanwhile, NBCUniversal's Peacock is launching without tentpole content like the Olympics or The Office. It's also yet to announce distribution deals with major streaming platforms.

The clock is ticking on competing services to win subscribers' attention. Disney continues to grow, bringing content originally slated for theatrical distribution to Disney+ to bolster its catalog and attract more subscribers. Netflix says it has a full pipeline of content that will keep its library fresh through the rest of the year to keep subscribers engaged. And Amazon Prime members are getting more value out of the service than ever.

Not only are the bigger services attracting more viewing hours, some major sports leagues will resume play soon, the weather is warm enough to spend more time outside, and governments are relaxing stay-at-home restrictions. The boom in streaming hours isn't expected to last indefinitely, and growth will slow considerably next year and the year after.

The path forward will get more difficult

Winning subscription streaming viewing is a difficult task already, and it's only going to get more difficult when growth in streaming hours slows down. Streamers are currently tasked with convincing consumers they will get good value from signing up for their service. 

As consumers' portfolio of services grows and the need for additional entertainment options declines, the task will become convincing consumers they should cancel one service and sign up for another. That's asking a lot from consumers, who typically take the path of least resistance.

Comcast's strategy to reduce friction for customers is to bundle Peacock with pay-TV subscriptions. It's already partnered with Cox to provide Peacock to its subscribers as well as Comcast's TV and internet subscribers. AT&T did something similar for HBO Max; if you already subscribe to HBO through your cable provider, you now have access to HBO Max. Just log in with your existing credentials. But that strategy fails in an environment with accelerating cord-cutting.

If customers have to make a choice about what streaming services they want, given a growing number of choices, their easiest option is no choice. They'll keep the services they have -- they were happy with those decisions, after all -- and with all their couch time accounted for, they probably won't be inclined to sign up for a lot of new services.