Strikes last a few days usually or weeks - indicatively per https://www.euronews.com/next/2023/03/07/industrial-action-in-france-and-the-uk-which-countries-have-the-most-strikes-in-europe
the highest national average per 1000 workers in certain European countries is something between $50$ and $150$ days, meaning less than a day per worker annually.
On the other hand, a wage increase tends in most cases to stay.
To see that purely income considerations makes a strike really likely, let's consider a greatly simplified exercise.
First, let's think in terms of weeks.
Let $W_0$ be the weekly wage without a strike and $E(W_s)$ be the expected weekly wage that the employer is expected to concede after a strike. Let $\beta <1 $ be the gross discount factor but the weekly one, which is a critical aspect of the situation.
The discounted stream of income without a strike is
$$I_0 = \sum_{t=0}^{\infty} \beta^t W_0 = W_0\cdot (1 + \beta + \beta^2 + ...) = \frac{1}{1-\beta}W_0 \tag{1}$$
while the discounted stream of income given a strike that will last $S$ weeks (so $S$ weeks without income), is
$$I_s = \sum_{t={S+1}}^{\infty} \beta^t E(W_s) = E(W_s)\cdot \big[\frac{1}{1-\beta} - (1 + \beta + \beta^2 +...+ \beta^S)\big]$$
$$=E(W_s) \cdot \left[\frac{1}{1-\beta} - \frac{1-\beta^{S+1}}{1-\beta}\right] = \frac{\beta^{S+1}}{1-\beta}E(W_s) \tag{2} $$
In terms of discounted income only, a strike gives more if
$$I_s > I_0 \implies \frac{\beta^{S+1}}{1-\beta}E(W_s) > \frac{1}{1-\beta}W_0 \implies E(W_s) > \frac 1 {\beta^{S+1}} W_0 \tag{3}$$
Now comes the crucial aspect that $\beta$ is a weekly discount factor, so it will be very close to unity.
For example to be consistent with a yearly $\beta_{yearly} = .9$ (which is considered a high degree of discounting the future, even for individuals), we must have $\beta = 0.9979758875215$ looking at $52$ weeks.
Suppose the strike lasts 1 week so $S=1$. Then the strike is beneficial for the workers if
$$E(W_s) > \frac 1 {(0.9979758875215)^{2}} W_0 = 1.00406054930652 \cdot W_0 \tag{4}$$
This means that even if the expected increase in the wage is just $0.5 \%$ (namely half a percentage point), the strike is beneficial - income wise. Note that this would be also the overall increase in the yearly income (this percentage does not compound week-by-week).
Considering striking for two weeks $S=2$, still does not raise this wage-increase-threshold above $1\%$. One needs to consider a strike that will last a month ($S=4$) to obtain that one needs to anticipate at least a $1\%$ increase in the wage for the strike to be beneficial in discounted income terms.
Of course, things in real life are much more complicated -for example, the above exercise implicitly assumes zero probability of being fired/losing employment.
Even if we changed the "infinite" horizon to a two-year one, then we would get that we need an expected wage increase after a one-week strike of just ~$2\%$.
The point I want to stress is that, purely income-wise, the situation is inherently "in favor" of going on strike, because even small wage increases make it worthwhile, which also indicates why employers resist even small wage increases (either profit-seeking private firms or budget-constrained public sector organizations).
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RESPONSE TO COMMENT ON MATHEMATICAL ISSUE
(for $\beta < 1$)
$$A \equiv 1+ \beta + \beta^2 + \dots +\beta^{S} \tag{a}$$
Take $(1/\beta)$ as a common factor in the right-hand-side,
$$A = \frac 1{\beta} \left(\beta + \beta^2 + \dots +\beta^{S+1}\right) \implies \beta A = \beta + \beta^2 + \dots +\beta^{S+1}. \tag{b}$$
Subtract $(b)$ from $(a)$
$$A - \beta A = 1+ \beta + \beta^2 + \dots +\beta^{S} - (\beta + \beta^2 + \dots +\beta^{S+1})$$
$$\implies (1-\beta)A = 1 - \beta^{S+1} \implies A = \frac{1 - \beta^{S+1}}{(1-\beta)}$$
