If someone is an esports player, it would be hard to stay a professional (in most action games at least) at age 30 simply due to natural wear on your hands and reaction times getting slower.
I doubt the boredom thing is that different for sports vs eSports. At least with eSports the game is changing due to patches. With sports, the game itself hardly changes.
For citation: see https://journals.plos.org/plosone/article?id=10.1371/journal... you can see reaction time starts to drop off rapidly starting at age 25
eSports players spend a lot more time playing than normal athletes. You can only be physically active for a few hours per day. eSports players can do a lot more, like tyler1 who consistently streams for 10+ hours 5 days a week.
Normal athletes arguably also get more variation. Football players don't play back to back football matches all day every day, they practice and improve in a lot of other ways. They also get more variation due to traveling around to play away games.
In CS:GO there were players around their 30s and were successful
https://liquipedia.net/counterstrike/Virtus.pro
e.g
>2016-07-30 1st S-Tier Offline ELEAGUE ELEAGUE Season 1 2 : 0 Fnatic $400,000
There is also societal stigma from playing video games seriously past early 20s(well atleast 5-10+ years ago, but with Twitch and things it is now way more accceptable).
"Reaction times in traditional sports are not as important" is laughable.
2. The athletes who do play "past their prime" are usually making up for reduced physical acuity with other skills (e.g. you don't see very many baseball players hit triples after 30).
3. Players with long careers invest a huge amount of time in conditioning, and to a hard-to-measure degree, PEDs.
4. I don't really follow eSports; If someone played Starcraft competitively 20 years ago, are they still playing SC, or do they switch to something else like LoL? What's the typical competitive "lifetime" of a game? If you picked up game-specific skills, it might be harder to apply #2 when the game du-jour changes.
5. As a slight nitpick to the whole conversation, my understanding is that "reaction time" is perhaps a misnomer; the drop in reaction time with age for performing a simple activity appears to be relatively minor, but more complex activities (including habitual ones like driving), which suggests that the performance decline is in selecting and/or executing the proper response to a stimuli rather than what we think of as pure "reaction time"
In e-sports there's millions of people practicing every day and the built in ranking system can filter that down to the current top 0.1%. At this point branching out into actual competitions is not nearly as difficult as getting noticed by a NBA, NFL, etc. recruiter.
It does depend on the Game. CSGO players play a very limited number of maps so pure reaction time and hand-eye coordination is often the deciding factor. Strategy games like LoL and softer FPS games like Fortnite are less dependent on physical talent.
The only ones that I know of are Quake and Street Fighter. In Quake currently only 1 or 2 of the best mechanically gifted players in the world are under 30. In Street Fighter, there's a wide range of ages including younger players as well as players as old as 40+. The "god of execution" Sakonoko is 42 years old and is still winning major tournaments every once in a while.
In Formula 1, Lewis Hamilton is likely on his way to yet another world championship at 36, edging it out over his 10 years younger contender.
https://liquipedia.net/counterstrike/Virtus.pro
e.g
>2016-07-30 1st S-Tier Offline ELEAGUE ELEAGUE Season 1 2 : 0 Fnatic $400,000