I’m seeing a lot of photos on social media of Israelis in Tel Aviv and
it’s suburbs hiding in bomb shelters during Gaza rocket launches,
which seemingly implies a relatively high chance of their house
getting hit by a rocket.
This is not what it implies. Since 1951, it's been part of Israeli law that "all homes, residential buildings and industrial buildings in Israel are required to have bomb shelters." (quote from Wikipedia).
Also, prior to 2011, when Israel's Iron Dome missile defense system was put in place, that now intercepts roughly 90% of incoming missiles targeted at Israel, the risk was much higher, and the lion's share of buildings in Tel Aviv were built prior to 2011.
While it is hard to pin down (e.g. the number of rocket attacks varies widely from year to year, the range of the rockets has varied over time, and the effectiveness of the Iron Dome has improved over time), we can look at some facts to provide an order of magnitude estimate.
The population of Tel Aviv is about 436,000, which is about 5% of the population is Israel proper excluding the West Bank and Gaza, and an estimate of the impact of a major earthquake's impact estimated that more than 330,000 buildings in Israel would suffer serious damage in an earthquake. It wouldn't be grossly off base to estimate that there are 20,000-50,000 buildings in Tel Aviv (fairly low since lots of housing in Tel Aviv is in the form of apartments with an average of 30 people or so per apartment building, and its office space is fairly high density as well).
According to Wikipedia:
Attacks began in 2001. Since then (August 2014 data), almost 20,000
rockets have hit southern Israel, all but a few thousand of them since
Israel withdrew from the Gaza Strip in August 2005. Hamas justified
these as counter-attacks to the Israeli blockade of Gaza. The rockets
have killed 28 people and injured hundreds more. The range of the
rockets has increased over time. The original Qassam rocket has a
range of about 10 km (6.2 mi) but more advanced rockets, including
versions of the old Soviet Grad or Katyusha have hit Israeli targets
40 km (25 mi) from Gaza.
Some rocket attacks damage buildings without causing death or injury to anyone. But, of course, the list above doesn't localize precisely where those rockets hit to an area as specific as Tel Aviv. One can look at the map to help gauge this fact as well:

Tel Aviv is about 70 km from the Gaza Strip, which is beyond the range of the vast majority of missiles and rockets fired from the Gaza Strip, and today, about 90% of income missiles and rockets are intercepted before reaching their targets. The distance from the Lebanese border from which Hezbollah frequently shoots missiles at Israel to Tel Aviv is roughly 110-120 km (crudely measuring the distance as the crow flies from the map).
So, a rough order of magnitude estimate would be that less than one in 10,000 buildings in Tel Aviv are likely to be struck by missiles or rockets in any given year. Few buildings were hit there in past years, because the lion's share of missiles and rockets launched towards Israel have lacked the range to hit Tel Aviv.
But, since the longest range missiles and rockets that exist in the international arms markets that could include Tel Aviv is non-zero, and the possibility of longer range missiles has grown in recent years (some were fired from Yemen but intercepted before striking Israeli targets in the past month) the risk in Tel Aviv is probably higher now than it has been in most of the last quarter-century.
The example of long range missile attacks from Russia to the deep interior of Ukraine illustrates the potential risk with current military technologies. Given that Iran and Syria both have military ties to Russia, and that some missiles of that type have been fired at Israel from Yemen, the prospect of those kinds of missiles being used against Israel and reaching Tel Aviv is far more than speculative.